Human lambda light chain mice

ABSTRACT

Genetically modified mice are provided that express human λ variable (hVλ) sequences, including mice that express hVλ sequences from an endogenous mouse λ light chain locus, mice that express hVλ sequences from an endogenous mouse κ light chain locus, and mice that express hVλ sequences from a transgene or an episome wherein the hVλ sequence is linked to a mouse constant sequence. Mice are provided that are a source of somatically mutated human λ variable sequences useful for making antigen-binding proteins. Compositions and methods for making antigen-binding proteins that comprise human λ variable sequences, including human antibodies, are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/604,021, filed May 24, 2017, which is a is a continuation of U.S.patent application Ser. No. 15/398,410, which is a continuation of U.S.patent application Ser. No. 14/943,890, filed Nov. 17, 2015, which is acontinuation of U.S. patent application Ser. No. 14/800,263, filed onJul. 15, 2015, which is a continuation of U.S. patent application Ser.No. 14/638,429, filed Mar. 4, 2015, which is a continuation of U.S.patent application Ser. No. 13/945,582, filed Jul. 18, 2013, which is adivisional of U.S. patent application Ser. No. 13/166,171, filed 22 Jun.2011, which claims the benefit under 35 USC § 119(e) of U.S. ProvisionalApplication Ser. No. 61/357,317, filed 22 Jun. 2010 and U.S. ProvisionalApplication Ser. No. 61/357,314, filed 22 Jun. 2010, each of which arehereby incorporated by reference in their entirety.

FIELD

Genetically modified mice that comprise a mouse or human lambda variable(Vλ) light chain sequence operably linked with a mouse or human lightchain constant region (λ or kappa(κ)). Genetically modified mice thatexpress epitope-binding proteins that comprise an immunoglobulin lightchain comprising a variable domain derived from a human lambda variable(hVλ) gene segment, a human lambda J (hJλ) gene segment, and a mouselight chain constant (C_(L)) domain. Genetically modified mice,comprising an unrearranged immunoglobulin lambda (λ) light chainvariable nucleic acid sequence at an endogenous mouse light chain locus.Mice capable of rearranging and expressing a chimeric human λ/mouseC_(L) light chain from an endogenous light chain locus that comprises areplacement of all endogenous mouse light chain variable region genesegments with one or more hVλ gene segments and one or more hJλ genesegments. Somatically mutated antibodies comprising hVλ domains andmouse C_(L) domains.

BACKGROUND

Mice that express antibodies that are fully human, or partly human andpartly mouse, are known in the art. For example, transgenic mice thatexpress fully human antibodies from transgenes containing human lightand heavy chain immunoglobulin variable region genes have been reported.Genetically modified mice that comprise a replacement of the endogenousmouse heavy chain variable region (HCVR) gene segments and kappa (κ)light chain variable region (LCVR) gene segments with human HCVR andLCVR gene segments and that make chimeric antibodies with a chimerichuman/mouse kappa chain are known as well.

Antibody light chains are encoded by one of two separate loci: kappa (κ)and lambda (λ). Mouse antibody light chains are primarily of the κ type.The ratio of κ to λ light chain usage in humans is about 60:40, whereasin mice it is about 95:5. Biased usage of κ light chains in mice isreportedly sustained in genetically modified mice capable of expressingfully or partly human antibodies. Thus, mice that express fully orpartly human antibodies appear to be constrained in lambda variableusage.

There is a need in the art to generate lambda variable regions, whethermouse or human, for use in making epitope-binding proteins. There is aneed in the art for mice that express fully or partly human antibodies,wherein the mice display an increased lambda variable (Vλ) usage.

There is a need in the art for mice that express fully or partly humanantibodies, wherein the mice display an increased λ variable (Vλ) usage.

SUMMARY

Genetically modified mice, embryos, cells, tissues, as well as nucleicacid constructs for modifying mice, and methods and compositions formaking and using them, are provided. Mice and cells that generate lambda(λ) variable regions (human or non-human) in the context of a kappa (κ)light chain are provided. Mice and cells that generate human λ variableregions in the context of a κ or a λ light chain, e.g., from anendogenous mouse light chain locus, are also provided. Also provided aremethods for making antibodies that comprise lambda variable regions.Methods for selecting heavy chains that express with cognate lambdavariable regions are also provided.

Chimeric and human antigen-binding proteins (e.g., antibodies), andnucleic acids encoding them, are provided that comprise somaticallymutated variable regions, including antibodies that have light chainscomprising a variable domain derived from a human Vλ and a human Jλ genesegment fused to a mouse light chain constant domain.

In one aspect, a mouse is provided that expresses a human λ variableregion sequence on a light chain that comprises a mouse constant region.In one aspect, a mouse is provided that expresses a human λ variableregion sequence on a light chain that comprises a κ constant region. Inone aspect, a mouse is provided that expresses from an endogenous mouselight chain locus a light chain that comprises a human λ variable regionsequence. In one aspect, a mouse is provided that comprises a rearrangedlight chain gene that comprises a human λ variable sequence linked to amouse constant region sequence; in one embodiment, the mouse constantregion sequence is a λ constant sequence; in one embodiment, the mouseconstant region sequence is a κ constant sequence.

In one aspect, a genetically modified mouse is provided, wherein themouse comprises an unrearranged human └ light chain variable genesegment (hVλ) and a human λ joining gene segment (hJλ). In oneembodiment, the unrearranged hVλ and hJλ are at a mouse light chainlocus. In one embodiment, the unrearranged hVλ and unrearranged hJλ areon a transgene and operably linked to a human or mouse constant regionsequence. In one embodiment, the unrearranged hVλ and unrearranged hJλare on an episome. In one embodiment, the mouse is capable of making animmunoglobulin that comprises a light chain that is derived from anunrearranged hVλ sequence and a hJλ sequence and a mouse light chainconstant region (C_(L)) nucleic acid sequence. Methods and compositionsfor making and using genetically modified mice are also provided.Antibodies are provided that comprise (a) a human heavy chain variabledomain (hV_(H)) fused to a mouse heavy chain constant region, and (b) ahuman Vλ fused to a mouse C_(L) domain; including wherein one or more ofthe variable domains are somatically mutated, e.g., during antibody orimmune cell selection in a mouse of the invention. In one embodiment,the unrearranged hVλ and unrearranged hJλ are operably linked with ahuman or mouse κ constant region (Cκ). In one embodiment, theunrearranged hVλ and unrearranged hJλ are operably linked with a humanor mouse λ constant region (Cλ).

In one aspect, a mouse is provided that comprises in its germline, at anendogenous mouse light chain locus, a human λ light chain variableregion sequence, wherein the human lambda variable region sequence isexpressed in a light chain that comprises a mouse immunoglobulinconstant region gene sequence.

In one embodiment, the endogenous mouse light chain locus is a λ locus.In one embodiment, the endogenous mouse light chain locus is a κ locus.

In one embodiment, the mouse lacks an endogenous light chain variablesequence at the endogenous mouse light chain locus.

In one embodiment, all or substantially all endogenous mouse light chainvariable region gene segments are replaced with one or more human λvariable region gene segments.

In one embodiment, the human λ light chain variable region sequencecomprises a human Jλ sequence. In one embodiment, the human Jλ sequenceis selected from the group consisting of Jλ1, Jλ2, Jλ3, Jλ7, and acombination thereof.

In one embodiment, the human λ light chain variable region sequencecomprises a fragment of cluster A of the human light chain locus. In aspecific embodiment, the fragment of cluster A of the human λ lightchain locus extends from hVλ3-27 through hVλ3-1.

In one embodiment, the human λ light chain variable region sequencecomprises a fragment of cluster B of the human light chain locus. In aspecific embodiment, the fragment of cluster B of the human λ lightchain locus extends from hVλ5-52 through hVλ1-40.

In one embodiment, the human λ light chain variable region sequencecomprises a genomic fragment of cluster A and a genomic fragment ofcluster B. In a one embodiment, the human λ light chain variable regionsequence comprises at least one gene segment of cluster A and at leastone gene segment of cluster B.

In one embodiment, more than 10% of the light chain naïve repertoire ofthe mouse is derived from at least two hVλ gene segments selected from2-8, 2-23, 1-40, 5-45, and 9-49. In one embodiment, more than 20% of thelight chain naïve repertoire of the mouse is derived from at least threehVλ gene segments selected from 2-8, 2-23, 1-40, 5-45, and 9-49. In oneembodiment, more than 30% of the light chain naïve repertoire of themouse is derived from at least four hVλ gene segments selected from 2-8,2-23, 1-40, 5-45, and 9-49.

In one aspect, a mouse is provided that expresses an immunoglobulinlight chain that comprises a human λ variable sequence fused with amouse constant region, wherein the mouse exhibits a κ usage to λ usageratio of about 1:1.

In one embodiment, the immunoglobulin light chain is expressed from anendogenous mouse light chain locus.

In one aspect, a mouse is provided that comprises a λ light chainvariable region sequence (Vλ) and at least one J sequence (J),contiguous with a mouse κ light chain constant region sequence.

In one embodiment, the mouse lacks a functional mouse Vκ and/or mouse Jκgene segment.

In one embodiment, the Vλ is a human Vλ (hVλ), and the J is a human Jλ(hJλ). In one embodiment, the hVλ and the hJλ are unrearranged genesegments.

In one embodiment, the mouse comprises a plurality of unrearranged hVλgene segments and at least one hJλ gene segment. In a specificembodiment, the plurality of unrearranged hVλ gene segments are at least12 gene segments, at least 28 gene segments, or at least 40 genesegments.

In one embodiment, the at least one hJλ gene segment is selected fromthe group consisting of Jλ1, Jλ2, Jλ3, Jλ7, and a combination thereof.

In one embodiment, an endogenous mouse λ light chain locus is deleted inwhole or in part.

In one embodiment, the mouse κ light chain constant region sequence isat an endogenous mouse κ light chain locus.

In one embodiment, about 10% to about 45% of the B cells of the mouseexpress an antibody that comprises a light chain comprising a human λlight chain variable (Vλ) domain and a mouse κ light chain constant (Cκ)domain.

In one embodiment, the human λ variable domain is derived from arearranged hVλ/hJλ sequence selected from the group consisting of 3-1/1,3-1/7, 4-3/1, 4-3/7, 2-8/1, 3-9/1, 3-10/1, 3-10/3, 3-10/7, 2-14/1,3-19/1, 2-23/1, 3-25/1, 1-40/1, 1-40/2, 1-40/3, 1-40/7, 7-43/1, 7-43/3,1-44/1, 1-44/7, 5-45/1, 5-45/2, 5-45/7, 7-46/1, 7-46/2, 7-46/7, 9-49/1,9-49/2, 9-49/7 and 1-51/1.

In one embodiment, the mouse further comprises a human Vκ-Jκ intergenicregion from a human κ light chain locus, wherein the human Vκ-Jκintergenic region is contiguous with the Vλ sequence and the J sequence.In a specific embodiment, the human Vκ-Jκ intergenic region is placedbetween the Vλ sequence and the J sequence.

In one aspect, a mouse is provided that comprises (a) at least 12 to atleast 40 unrearranged human λ light chain variable region gene segmentsand at least one human Jλ gene segment at an endogenous mouse lightchain locus; (b) a human Vκ-Jκ intergenic sequence located between theat least 12 to at least 40 human light chain variable region genesegments and the at least one human Jλ sequence; wherein the mouseexpress an antibody that comprises a light chain comprising a human Vλdomain and a mouse Cκ domain.

In one aspect, a mouse is provided that expresses an antibody comprisinga light chain that comprises a λ variable sequence and a κ constantsequence.

In one embodiment, the mouse exhibits a κ usage to λ usage ratio ofabout 1:1.

In one embodiment, a population of immature B cells obtained from bonemarrow of the mouse exhibits a κ usage to λ usage ratio of about 1:1.

In one aspect, a genetically modified mouse is provided, wherein themouse comprises an unrearranged immunoglobulin Vλ and a Jλ gene segmentoperably linked to a mouse light chain locus that comprises a mouseC_(L) gene.

In one embodiment, the Vλ and/or Jλ gene segments are human genesegments. In one embodiment, the Vλ and/or Jλ gene segments are mousegene segments, and the C_(L) is a mouse Cκ.

In one embodiment, the endogenous mouse light chain locus is a κ lightchain locus. In one embodiment, the endogenous mouse light chain locusis a λ light chain locus.

In one embodiment, the unrearranged Vλ and Jλ gene segments are at anendogenous mouse light chain locus.

In one embodiment, the unrearranged immunoglobulin Vλ and Jλ genesegments are on a transgene.

In one embodiment, the mouse further comprises a replacement of one ormore heavy chain V, D, and/or J gene segments with one or more human V,D, and/or J gene segments at an endogenous mouse heavy chainimmunoglobulin locus.

In one embodiment, the mouse comprises an unrearranged immunoglobulin Vλand a Jλ gene segment at an endogenous mouse κ light chain locus thatcomprises a mouse OK gene.

In one embodiment, the mouse comprises an unrearranged humanimmunoglobulin λ light chain variable gene segment (Vλ) and a λ joininggene segment (Jλ) at an endogenous mouse λ light chain locus thatcomprises a mouse Cλ gene.

In one embodiment, the light chain variable gene locus (the “V_(L)locus”) comprises at least one human Vλ (hVλ) gene segment. In oneembodiment, the V_(L) locus comprises at least one human Jλ (hJλ) genesegment. In another embodiment, V_(L) locus comprises up to four hJλgene segments. In one embodiment, the V_(L) locus comprises a contiguoussequence comprising human λ and human κ genomic sequence.

In one embodiment, the κ light chain variable gene locus (the “κ locus”)comprises at least one human Vλ (hVλ) gene segment. In one embodiment,the κ locus comprises at least one human Jλ (hJλ) gene segment. In oneembodiment, the κ locus comprises up to four hJλ gene segments. In oneembodiment, the κ locus comprises at least one hVλ and at least one hJλ,and lacks or substantially lacks a functional Vκ region gene segment andlacks or substantially lacks a functional Jκ region gene segment. In oneembodiment, the mouse comprises no functional Vκ region gene segment. Inone embodiment, the mouse comprises no functional Jκ region genesegment.

In one embodiment, the λ light chain variable gene locus (the “λ locus”)comprises at least one hVλ gene segment. In one embodiment, the λ locuscomprises at least one human Jλ (hJλ) gene segment. In anotherembodiment, the λ locus comprises up to four hJλ gene segments.

In one embodiment, the V_(L) locus comprises a plurality of hVλs. In oneembodiment, the plurality of hVλs are selected so as to result inexpression of a λ light chain variable region repertoire that reflectsabout 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about70%, about 80%, or about 90% or more of the Vλ usage observed in ahuman. In one embodiment, the V_(L) locus comprises gene segments hVλ1-40, 1-44, 2-8, 2-14, 3-21, and a combination thereof.

In one embodiment, the hVλs include 3-1, 4-3, 2-8, 3-9, 3-10, 2-11, and3-12. In a specific embodiment, the V_(L) locus comprises a contiguoussequence of the human λ light chain locus that spans from Vλ3-12 toVλ3-1. In one embodiment, the V_(L) locus comprises at least 2, 3, 4, 5,6, 7, 8, 9, 10, 11 or 12 hVλs. In a specific embodiment, the hVλsinclude 3-1, 4-3, 2-8, 3-9, 3-10, 2-11, and 3-12. In a specificembodiment, the V_(L) locus comprises a contiguous sequence of the humanλ locus that spans from Vλ3-12 to Vλ3-1. In one embodiment, the V_(L)locus is at the endogenous κ locus. In a specific embodiment, the V_(L)locus is at the endogenous κ locus and the endogenous λ light chainlocus is deleted in part or completely. In one embodiment, the V_(L)locus is at the endogenous λ locus. In a specific embodiment, the V_(L)locus is at the endogenous λ locus and the endogenous κ locus is deletedin part or completely.

In one embodiment, the V_(L) locus comprises 13 to 28 or more hVλs. In aspecific embodiment, the hVλs include 2-14, 3-16, 2-18, 3-19, 3-21,3-22, 2-23, 3-25, and 3-27. In a specific embodiment, the κ locuscomprises a contiguous sequence of the human λ locus that spans fromVλ3-27 to Vλ3-1. In one embodiment, the V_(L) locus is at the endogenousκ locus. In a specific embodiment, the V_(L) locus is at the endogenousκ locus and the endogenous λ light chain locus is deleted in part orcompletely. In another embodiment, the V_(L) locus is at the endogenousλ locus. In a specific embodiment, the V_(L) locus is at the endogenousλ locus and the endogenous K locus is deleted in part or completely.

In one embodiment, the V_(L) locus comprises 29 to 40 hVλs. In aspecific embodiment, the κ locus comprises a contiguous sequence of thehuman λ locus that spans from Vλ3-29 to Vλ3-1, and a contiguous sequenceof the human λ locus that spans from Vλ5-52 to Vλ1-40. In a specificembodiment, all or substantially all sequence between hVλ1-40 andhVλ3-29 in the genetically modified mouse consists essentially of ahuman λ sequence of approximately 959 bp found in nature (e.g., in thehuman population) downstream of the hVλ1-40 gene segment (downstream ofthe 3′ untranslated portion), a restriction enzyme site (e.g., PI-Scel),followed by a human λ sequence of approximately 3,431 bp upstream of thehVλ3-29 gene segment found in nature. In one embodiment, the V_(L) locusis at the endogenous mouse κ locus. In a specific embodiment, the V_(L)locus is at the endogenous mouse κ locus and the endogenous mouse λlight chain locus is deleted in part or completely. In anotherembodiment, the V_(L) locus is at the endogenous mouse λ locus. In aspecific embodiment, the V_(L) locus is at the endogenous mouse λ locusand the endogenous mouse κ locus is deleted in part or completely.

In one embodiment, the V_(L) locus comprises at least one hJλ. In oneembodiment, the V_(L) locus comprises a plurality of hJλs. In oneembodiment, the V_(L) locus comprises at least 2, 3, 4, 5, 6, or 7 hJλ.In a specific embodiment, the V_(L) locus comprises four hJλ. In aspecific embodiment, the four hJλs are hJλ1, hJλ2, hJλ3, and hJλ7. Inone embodiment, the V_(L) locus is a κ locus. In a specific embodiment,the V_(L) locus is at the endogenous κ locus and the endogenous λ lightchain locus is deleted in part or completely. In one embodiment, theV_(L) locus comprises one hJλ. In a specific embodiment, the one hJλ ishJλ1. In one embodiment, the V_(L) locus is at the endogenous κ locus.In a specific embodiment, the V_(L) locus is at the endogenous κ locusand the endogenous λ light chain locus is deleted in part or completely.In another embodiment, the V_(L) locus is at the endogenous λ locus. Ina specific embodiment, the V_(L) locus is at the endogenous λ locus andthe endogenous κ locus is deleted in part or completely.

In one embodiment, the V_(L) locus comprises at least one hVλ, at leastone hJλ, and a mouse C| gene. In one embodiment, the V_(L) locuscomprises at least one hVλ, at least one hJλ, and a mouse Cλ gene. In aspecific embodiment, the mouse Cλ gene is Cλ2. In a specific embodiment,the mouse Cλ gene is at least 60%, at least 70%, at least 80%, at least90%, at least 95%, 96%, 97%, 98%, or at least 99% identical to mouseCλ2.

In one embodiment, the mouse comprises a replacement at the endogenousmouse κ locus of endogenous mouse Vκ gene segments with one or more hVλgene segments, wherein the hVλ gene segments are operably linked to anendogenous mouse Cκ region gene, such that the mouse rearranges thehuman Vλ gene segments and expresses a reverse chimeric immunoglobulinlight chain that comprises a human Vλ domain and a mouse Cκ. In oneembodiment, 90-100% of unrearranged mouse Vκ gene segments are replacedwith at least one unrearranged hVλ gene segment. In a specificembodiment, all or substantially all of the endogenous mouse Vκ genesegments are replaced with at least one unrearranged hVλ gene segment.In one embodiment, the replacement is with at least 12, at least 28, orat least 40 unrearranged hVλ gene segments. In one embodiment, thereplacement is with at least 7 functional unrearranged hVλ genesegments, at least 16 functional unrearranged hVλ gene segments, or atleast 27 functional unrearranged hVλ gene segments. In one embodiment,the mouse comprises a replacement of all mouse Jκ gene segments with atleast one unrearranged hJλ gene segment. In one embodiment, the at leastone unrearranged hJλ gene segment is selected from Jλ1, Jλ2, Jλ3, Jλ4,JλS, Jλ6, Jλ7, and a combination thereof. In a specific embodiment, theone or more hVλ gene segment is selected from a 3-1, 4-3, 2-8, 3-9,3-10, 2-11, 3-12, 2-14, 3-16, 2-18, 3-19, 3-21, 3-22, 2-23, 3-25, 3-27,1-40, 7-43, 1-44, 5-45, 7-46, 1-47, 5-48, 9-49, 1-50, 1-51, a 5-52 hVλgene segment, and a combination thereof. In a specific embodiment, theat least one unrearranged hJλ gene segment is selected from Jλ1, Jλ2,Jλ3, Jλ7, and a combination thereof.

In one embodiment, the mouse comprises a replacement of endogenous mouseVλ gene segments at the endogenous mouse λ locus with one or more humanVλ gene segments at the endogenous mouse λ locus, wherein the hVλ genesegments are operably linked to a mouse Cλ region gene, such that themouse rearranges the hVλ gene segments and expresses a reverse chimericimmunoglobulin light chain that comprises a hVλ domain and a mouse Cλ.In a specific embodiment, the mouse Cλ gene is Cλ2. In a specificembodiment, the mouse Cλ gene is at least 60%, at least 70%, at least80%, at least 90%, at least 95%, or at least 98% identical to mouse Cλ2.In one embodiment, 90-100% of unrearranged mouse Vλ gene segments arereplaced with at least one unrearranged hVλ gene segment. In a specificembodiment, all or substantially all of the endogenous mouse Vλ genesegments are replaced with at least one unrearranged hVλ gene segment.In one embodiment, the replacement is with at least 12, at least 28, orat least 40 unrearranged hVλ gene segments. In one embodiment, thereplacement is with at least 7 functional unrearranged hVλ genesegments, at least 16 functional unrearranged hVλ gene segments, or atleast 27 functional unrearranged hVλ gene segments. In one embodiment,the mouse comprises a replacement of all mouse Jλ gene segments with atleast one unrearranged hJλ gene segment. In one embodiment, the at leastone unrearranged hJλ gene segment is selected from Jλ1, Jλ2, Jλ3, Jλ4,JλS, Jλ6, Jλ7, and a combination thereof. In a specific embodiment, theone or more hVλ gene segment is selected from a 3-1, 4-3, 2-8, 3-9,3-10, 2-11, 3-12, 2-14, 3-16, 2-18, 3-19, 3-21, 3-22, 2-23, 3-25, 3-27,1-40, 7-43, 1-44, 5-45, 7-46, 1-47, 5-48, 9-49, 1-50, 1-51, a 5-52 hVλgene segment, and a combination thereof. In a specific embodiment, theat least one unrearranged hJλ gene segment is selected from Jλ1, Jλ2,Jλ3, Jλ7, and a combination thereof.

In one aspect, a genetically modified mouse is provided that comprises ahuman Vκ-Jκ intergenic region sequence located at an endogenous mouse κlight chain locus.

In one embodiment, the human Vκ-Jκ intergenic region sequence is at anendogenous κ light chain locus of a mouse that comprises a hVλ and hJλgene segment, and the human Vκ-Jκ intergenic region sequence is disposedbetween the hVλ and hJλ gene segments. In a specific embodiment, the hVλand hJλ gene segments are capable of recombining to form a functionalhuman λ light chain variable domain in the mouse.

In one embodiment, a mouse is provided that comprises a plurality ofhVλ's and one or more hJλ's, and the human Vκ-Jκ intergenic regionsequence is disposed, with respect to transcription, downstream of theproximal or 3′ most hVλ sequence and upstream or 5′ of the first hJλsequence.

In one embodiment, the human Vκ-Jκ intergenic region is a region locatedabout 130 bp downstream or 3′ of a human Vκ4-1 gene segment, about 130bp downstream of the 3′ untranslated region of the human Vκ4-1 genesegment, and spans to about 600 bp upstream or 5′ of a human Jκ1 genesegment. In a specific embodiment, the human Vκ-Jκ intergenic region isabout 22.8 kb in size. In one embodiment, the Vκ-Jκ intergenic region isabout 90% or more, 91% or more, 92% or more, 93% or more, 94% or more,or about 95% or more identical with a human Vκ-Jκ intergenic regionextending from the end of the 3′ untranslated region of a human Vκ4-1gene segment to about 600 bp upstream of a human Jκ1 gene segment. Inone embodiment, the Vκ-Jκ intergenic region comprises SEQ ID NO:100. Ina specific embodiment, the Vκ-Jκ intergenic region comprises afunctional fragment of SEQ ID NO:100. In a specific embodiment, theVκ-Jκ intergenic region is SEQ ID NO:100.

In one aspect, a mouse, a mouse cell (e.g., a mouse embryonic stemcell), a mouse embryo, and a mouse tissue are provided that comprise therecited human Vκ-Jκ intergenic region sequence, wherein the intergenicregion sequence is ectopic. In a specific embodiment, the ectopicsequence is placed at a humanized endogenous mouse immunoglobulin locus.

In one aspect, an isolated nucleic acid construct is provided thatcomprises the recited human Vκ-Jκ intergenic region sequence. In oneembodiment, the nucleic acid construct comprises targeting arms totarget the human Vκ-Jκ intergenic region sequence to a mouse light chainlocus. In a specific embodiment, the mouse light chain locus is a κlocus. In a specific embodiment, the targeting arms target the humanVκ-Jκ intergenic region to a modified endogenous mouse κ locus, whereinthe targeting is to a position between a hVλ sequence and a hJλsequence.

In one aspect, a genetically modified mouse is provided, wherein themouse comprises no more than two light chain alleles, wherein the lightchain alleles comprise (a) an unrearranged immunoglobulin human Vλ and aJλ gene segment at an endogenous mouse light chain locus that comprisesa mouse C_(L) gene; and, (b) an unrearranged immunoglobulin V_(L) and aJ_(L) gene segment at an endogenous mouse light chain locus thatcomprises a mouse C_(L) gene.

In one embodiment, the endogenous mouse light chain locus is a κ locus.In another embodiment, the endogenous mouse light chain locus is a λlocus.

In one embodiment, the no more than two light chain alleles are selectedfrom a κ allele and a λ allele, two κ alleles, and two λ alleles. In aspecific embodiment, one of the two light chain alleles is a λ allelethat comprises a Cλ2 gene.

In one embodiment, the mouse comprises one functional immunoglobulinlight chain locus and one nonfunctional light chain locus, wherein thefunctional light chain locus comprises an unrearranged immunoglobulinhuman Vλ and a Jλ gene segment at an endogenous mouse κ light chainlocus that comprises a mouse Cκ gene.

In one embodiment, the mouse comprises one functional immunoglobulinlight chain locus and one nonfunctional light chain locus, wherein thefunctional light chain locus comprises an unrearranged immunoglobulinhuman Vλ and a Jλ gene segment at an endogenous mouse λ light chainlocus that comprises a mouse Cλ gene. In one embodiment, the Cλ gene isCλ2. In a specific embodiment, the mouse Cλ gene is at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%, or at least 98%identical to mouse Cλ2.

In one embodiment, the mouse further comprises at least oneimmunoglobulin heavy chain allele. In one embodiment, the at least oneimmunoglobulin heavy chain allele comprises a human V_(H) gene segment,a human D_(H) gene segment, and a human J_(H) gene segment at anendogenous mouse heavy chain locus that comprises a human heavy chaingene that expresses a human/mouse heavy chain. In a specific embodiment,the mouse comprises two immunoglobulin heavy chain alleles, and themouse expresses a human/mouse heavy chain.

In one embodiment, the mouse comprises a first light chain allele thatcomprises an unrearranged hVκ and an unrearranged hJκ, at an endogenousmouse κ locus that comprises an endogenous Cκ gene; and a second lightchain allele that comprises an unrearranged hVλ and an unrearranged hJλ,at an endogenous mouse κ locus that comprises an endogenous Cκ gene. Ina specific embodiment, the first and the second light chain alleles arethe only functional light chain alleles of the genetically modifiedmouse. In a specific embodiment, the mouse comprises a nonfunctional λlocus. In one embodiment, the genetically modified mouse does notexpress a light chain that comprises a λ constant region.

In one embodiment, the mouse comprises a first light chain allele thatcomprises an unrearranged hVκ and an unrearranged hJκ, at an endogenousmouse κ locus that comprises an endogenous Cκ gene; and a second lightchain allele that comprises an unrearranged hVλ and an unrearranged hJλ,at an endogenous mouse λ locus that comprises an endogenous Cλ gene. Ina specific embodiment, the first and the second light chain alleles arethe only functional light chain alleles of the genetically modifiedmouse. In one embodiment, the endogenous Cλ gene is Cλ2. In a specificembodiment, the mouse Cλ gene is at least 60%, at least 70%, at least80%, at least 90%, at least 95%, or at least 98% identical to mouse Cλ2.

In one embodiment, the mouse comprises six immunoglobulin alleles,wherein the first allele comprises an unrearranged immunoglobulin Vλ andJλ gene segment at an endogenous mouse κ light chain locus thatcomprises a mouse Cκ gene, the second comprises an unrearrangedimmunoglobulin Vκ and Jκ gene segment at an endogenous mouse κ lightchain locus that comprises a mouse Cκ gene, the third comprises anunrearranged immunoglobulin Vλ and Jλ gene segment at an endogenousmouse λ light chain locus that comprises a mouse Cλ gene, the fourth andfifth each independently comprise an unrearranged V_(H) and D_(H) andJ_(H) gene segment at an endogenous mouse heavy chain locus thatcomprises a mouse heavy chain gene, and the sixth comprises either (a)an unrearranged immunoglobulin Vλ and Jλ gene segment at an endogenousmouse λ light chain locus that comprises a mouse Cλ gene, (b) a λ locusthat is nonfunctional, or (c) a deletion in whole or in part of the λlocus.

In one embodiment, the first allele comprises an unrearranged hVλ andhJλ. In one embodiment, the second allele comprises an unrearranged hVκand hJκ. In one embodiment, the third allele comprises an unrearrangedhVλ and hJλ. In one embodiment, the fourth and fifth each independentlycomprise an unrearranged hV_(H) and hD_(H) and hJ_(H). In oneembodiment, the sixth allele comprises an endogenous mouse λ locus thatis deleted in whole or in part.

In one embodiment, the mouse comprises six immunoglobulin alleles,wherein the first allele comprises an unrearranged immunoglobulin Vλ andJλ gene segment at an endogenous mouse λ light chain locus thatcomprises a mouse Cλ gene, the second comprises an unrearrangedimmumoglobulin Vλ and Jλ gene segment at an endogenous mouse λ lightchain locus that comprises a mouse Cλ gene, the third comprises anunrearranged immunoglobulin Vκ and Jκ gene segment at an endogenousmouse κ light chain locus that comprises a mouse Cκ gene, the fourth andfifth each independently comprise an unrearranged V_(H) and D_(H) andJ_(H) gene segment at an endogenous mouse heavy chain locus thatcomprises a mouse heavy chain gene, and the sixth comprises either (a)an unrearranged immunoglobulin Vκ and Jκ gene segment at an endogenousmouse κ light chain locus that comprises a mouse Cκ gene, (b) a κ locusthat is nonfunctional, or (c) a deletion of one or more elements of theκ locus.

In one embodiment, the first allele comprises an unrearranged hVλ andhJλ gene segment. In one embodiment, the second allele comprises anunrearranged hVλ and hJλ gene segment. In one embodiment, the thirdallele comprises an unrearranged hVκ and hJκ gene segment. In oneembodiment, the fourth and fifth each independently comprise anunrearranged hV_(H) and hD_(H) and hJ_(H) gene segment. In oneembodiment, the sixth allele comprises an endogenous mouse κ locus thatis functionally silenced.

In one embodiment, the genetically modified mouse comprises a B cellthat comprises a rearranged antibody gene comprising a rearranged hVλdomain operably linked to a mouse C_(L) domain. In one embodiment, themouse C_(L) domain is selected from a mouse Cκ and a mouse Cλ domain. Ina specific embodiment, the mouse Cλ domain is derived from a Cλ2 gene.In a specific embodiment, the mouse Cλ domain is derived from a Cλdomain that is at least 60%, at least 70%, at least 80%, at least 90%,at least 95%, or at least 98% identical to mouse Cλ2.

In one aspect, a genetically modified mouse is provided that expresses aVλ region on a C_(L) that is a Cκ. In one aspect, a genetically modifiedmouse is provided that expresses a hVλ region on a C_(L) selected from ahuman Cκ, a human Cλ, or a mouse Cκ. In one aspect, a geneticallymodified mouse is provided that expresses a hVλ region on a mouse Cκ.

In one embodiment, about 10-50% of the splenocytes of the mouse are Bcells (i.e., CD19-positive), or which about 9-28% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In a specific embodiment, about 23-34% of the splenocytes of the mouseare B cells (i.e., CD19-positive), or which about 9-11% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In a specific embodiment, about 19-31% of the splenocytes of the mouseare B cells (i.e., CD19-positive), or which about 9-17% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In a specific embodiment, about 21-38% of the splenocytes of the mouseare B cells (i.e., CD19-positive), or which about 24-27% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In a specific embodiment, about 10-14% of the splenocytes of the mouseare B cells (i.e., CD19-positive), or which about 9-13% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In a specific embodiment, about 31-48% of the splenocytes of the mouseare B cells (i.e., CD19-positive), or which about 15-21% express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain. In a specific embodiment, about 30-38% of the splenocytes of themouse are B cells (i.e., CD19-positive), of which about 33-48% expressan immunoglobulin light chain comprising a hVλ domain fused to a mouseCκ domain.

In one embodiment, about 52-70% of the bone marrow of the mouse are Bcells (i.e., CD19-positive), or which about 31-47% of the immature Bcells (i.e., CD19-positive/B220-intermediate positive/IgM-positive)express an immunoglobulin light chain comprising a hVλ domain fused to amouse Cκ domain.

In one embodiment, about 60% of the bone marrow of the mouse are B cells(i.e., CD19-positive), or which about 38.3% of the immature B cells(i.e., CD19-positive/B220-intermediate positive/IgM-positive) express animmunoglobulin light chain comprising a hVλ domain fused to a mouse Cκdomain.

In one embodiment, the mouse expresses an antibody comprising a lightchain that comprises a variable domain derived from a human V and ahuman J gene segment, and a constant domain derived from a mouseconstant region gene. In one embodiment, the mouse constant region geneis a Cκ gene. In another embodiment, the mouse constant region gene is aCλ gene. In a specific embodiment, the Cλ region is Cλ2. In a specificembodiment, the mouse Cλ gene is derived from a Cλ gene that is at least60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least98% identical to mouse Cλ2. In a specific embodiment, the antibodyfurther comprises a heavy chain comprising a variable domain derivedfrom a human V, a human D and a human J gene segment, and a heavy chainconstant domain derived from a mouse heavy chain constant region gene.In one embodiment, the mouse heavy chain constant region gene comprisesa hinge-CH₂—CH₃ sequence of a heavy chain constant domain. In anotherembodiment, the mouse heavy chain constant region gene comprises aCH₁-hinge-CH₂—CH₃ sequence of a heavy chain constant domain. In anotherembodiment, the mouse heavy chain constant region gene comprises aCH₁—CH₂—CH₃—CH₄ sequence of a heavy chain constant domain. In anotherembodiment, the mouse heavy chain constant region gene comprises aCH₂—CH₃—CH₄ sequence of a heavy chain constant domain.

In one embodiment, the mouse expresses an antibody comprising a lightchain that comprises a rearranged human Vλ-Jλ sequence and a mouse Cκsequence. In one embodiment, the rearranged human Vλ-Jλ sequence isderived from a rearrangement of hVλ gene segments selected from a 3-1,4-3, 2-8, 3-9, 3-10, 2-14, 3-19, 2-23, 3-25, 1-40, 7-43, 1-44, 5-45,7-46, 1-47, 9-49, and a 1-51 gene segment. In one embodiment, therearranged human Vλ-Jλ sequence is derived from a rearrangement of hJλgene segments selected from Jλ1, Jλ2, Jλ3, and a Jλ7 gene segment.

In one embodiment, the mouse expresses an antibody comprising a lightchain that comprises a rearranged immunoglobulin λ light chain variableregion comprising a human Vλ/Jλ sequence selected from 3-1/1, 3-1/7,4-3/1, 4-3/7, 2-8/1, 3-9/1, 3-10/1, 3-10/3, 3-10/7, 2-14/1, 3-19/1,2-23/1, 3-25/1, 1-40/1, 1-40/2, 1-40/3, 1-40/7, 7-43/1, 7-43/3, 1-44/1,1-44/7, 5-45/1, 5-45/2, 5-45/7, 7-46/1, 7-46/2, 7-46/7, 9-49/1, 9-49/2,9-49/7 and 1-51/1. In a specific embodiment, the B cell expresses anantibody comprising a human immunoglobulin heavy chain variable domainfused with a mouse heavy chain constant domain, and a humanimmunoglobulin λ light chain variable domain fused with a mouse κ lightchain constant domain.

In one aspect, a mouse is provided that expresses an antibody comprising(a) a heavy chain comprising a heavy chain variable domain derived froman unrearranged human heavy chain variable region gene segment, whereinthe heavy chain variable domain is fused to a mouse heavy chain constant(C_(H)) region; and, (b) a light chain comprising a light chain variabledomain derived from an unrearranged hVλ and a hJλ, wherein the lightchain variable domain is fused to a mouse C_(L) region.

In one embodiment, the mouse comprises (i) a heavy chain locus thatcomprises a replacement of all or substantially all functionalendogenous mouse V, D and J gene segments with all or substantially allfunctional human V, D, and J gene segments, a mouse C_(H) gene, (ii) afirst κ light chain locus comprising a replacement of all orsubstantially all functional endogenous mouse Vκ and Jκ gene segmentswith all, substantially all, or a plurality of, functional hVλ and hJλgene segments, and a mouse C| gene, (iii) a second κ light chain locuscomprising a replacement of all or substantially all functionalendogenous mouse Vκ and Jκ gene segments with all, substantially all, ora plurality of, functional hVκ and hJκ gene segments, and a mouse Cκgene. In one embodiment, the mouse does not express an antibody thatcomprises a Cλ region. In one embodiment, the mouse comprises a deletionof a Cλ gene and/or a Vλ and/or a Jλ gene segment. In one embodiment,the mouse comprises a nonfunctional λ light chain locus. In a specificembodiment, the λ light chain locus is deleted in whole or in part.

In one embodiment, the mouse comprises (i) a heavy chain locus thatcomprises a replacement of all or substantially all functionalendogenous mouse V, D and J gene segments with all or substantially allfunctional human V, D, and J gene segments, a mouse C_(H) gene, (ii) afirst λ light chain locus comprising a replacement of all orsubstantially all functional endogenous mouse Vλ and Jλ gene segmentswith all, substantially all, or a plurality of, functional hVλ and hJλgene segments, and a mouse Cλ gene, (iii) a second λ light chain locuscomprising a replacement of all or substantially all functionalendogenous mouse Vλ and Jλ gene segments with all, substantially all, ora plurality of, functional hVλ and hJλ gene segments, and a mouse Cλgene. In a specific embodiment, the mouse Cλ gene is Cλ2. In a specificembodiment, the mouse Cλ gene is derived from a Cλ gene that is at least60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least98% identical to mouse Cλ2.

In one embodiment, the mouse comprises a deletion of a Cκ gene and/or aVκ and/or a Jκ gene segment. In one embodiment, the mouse comprises anonfunctional κ light chain locus.

In one aspect, a genetically modified mouse that expresses an antibodyis provided, wherein greater than 10%, greater than 15%, greater than20%, greater than 25%, greater than 30%, greater than 35%, greater than40%, greater than 60%, greater than 70%, greater than 80%, or greaterthan 90% of total IgG antibody produced by the mouse comprises aλ-derived variable domain, and wherein the mouse expresses antibodiescomprising a κ-derived variable domain fused with a mouse Cκ region. Inspecific embodiments, about 15-40%, 20-40%, 25-40%, 30-40%, or 35-40% oftotal antibody produced by the mouse comprises a λ-derived variabledomain.

In one embodiment, the λ-derived variable domain is derived from a hVλand a hJλ. In one embodiment, the λ-derived variable domain is in alight chain that comprises a mouse Cκ region. In a specific embodiment,the λ-derived variable region is in a light chain that comprises a mouseCλ region. In another specific embodiment, the Cλ region is a Cλ2region. In one embodiment, the κ-derived variable domain is derived froma hVκ and a hJκ, and in a specific embodiment is in a light chain thatcomprises a mouse Cκ region.

In one aspect, an isolated DNA construct is provided that comprises anupstream homology arm and a downstream homology arm, wherein theupstream and the downstream homology arms target the construct to amouse κ locus, and the construct comprises a functional unrearranged hVλsegment and a functional unrearranged hJλ segment, and a selection ormarker sequence.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting a mouse λ sequence upstream of mouse Vλ2, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites, and atargeting arm for targeting a mouse λ sequence 3′ of mouse Jλ2. In oneembodiment, the selection cassette is a Frt'ed Hyg-TK cassette. In oneembodiment, the 3′ targeting arm comprises mouse Cλ2, Jλ4, Cλ4, andmouse enhancer 2.4.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse λ locus 5′ with respect to Vλ1, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites, and a 3′targeting arm for targeting a mouse λ sequence 3′ with respect to mouseCλ1. In one embodiment, the selection cassette is a Ioxed neomycincassette. In one embodiment, the 3′ targeting arm comprises the mouse λ3′ enhancer and mouse λ 3′ enhancer 3.1.

In one aspect, an isolated DNA construct is provided, comprising from 5′to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse λ locus 5′ with respect to Vλ2, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites, and a 3′targeting arm for targeting a mouse λ sequence 3′ with respect to mouseJλ2 and 5′ with respect to mouse Cλ2. In one embodiment, the selectioncassette is a Frt'ed hygromycin-TK cassette. In one embodiment, the 3′targeting arm comprises the mouse Cλ2-Jλ4-Cλ4 gene segments and mouse λenhancer 2.4.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse λ locus 5′ with respect to Vλ2, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites, a humangenomic fragment comprising a contiguous region of the human λ lightchain locus from hVλ3-12 downstream to the end of hJλ1, and a 3′targeting arm for targeting a mouse λ sequence 3′ with respect to mouseJλ2. In one embodiment, the selection cassette is a Frt'ed neomycincassette. In one embodiment, the 3′ targeting arm comprises the mouseCλ2-Jλ4-Cλ4 gene segments and mouse λ enhancer 2.4.

In one aspect, an isolated DNA construct is provided, comprising acontiguous region of the human λ light chain locus from hVλ3-12downstream to the end of hJλ1.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse λ locus 5′ with respect to Vλ2, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites and ahuman genomic fragment comprising a contiguous region of the human λlight chain locus from hVλ3-27 downstream to the end of hVλ2-8. In oneembodiment, the selection cassette is a Frt'ed hygromycin cassette. Inone embodiment, the human genomic fragment comprises a 3′ targeting arm.In a specific embodiment, the 3′ targeting arm comprises about 53 kb ofthe human λ light chain locus from hVλ3-12 downstream to the end ofhVλ2-8.

In one aspect, an isolated DNA construct is provided, comprising acontiguous region of the human λ light chain locus from hVλ3-27downstream to the end of hVλ3-12.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse λ locus 5′ with respect to Vλ2, a selectioncassette flanked 5′ and 3′ with recombinase recognition sites, a firsthuman genomic fragment comprising a contiguous region of the human λlight chain locus from hVλ5-52 downstream to the end of hVλ1-40, arestriction enzyme site, and a second human genomic fragment comprisinga contiguous region of the human λ light chain locus from hVλ3-29downstream to the end of hVλ82K. In one embodiment, the selectioncassette is a Frt'ed neomycin cassette. In one embodiment, therestriction enzyme site is a site for a homing endonuclease. In aspecific embodiment, the homing endonuclease is PI-Scel. In onembodiment, the second human genomic fragment is a 3′ targeting arm. Ina specific embodiment, the 3′ targeting arm comprises about 27 kb of thehuman λ light chain locus from hVλ3-29 downstream to the end of hVλ82K.

In one aspect, an isolated DNA construct is provided, comprising acontiguous region of the human λ light chain locus from hVλ5-52downstream to the end of hVλ1-40.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse κ locus 5′ with respect to the endogenous Vκgene segments, two juxtaposed recombinase recognition sites, a selectioncassette 3′ to the juxtaposed recombinase recognition sites, and a 3′targeting arm for targeting a mouse κ sequence 5′ with respect to the κlight chain variable gene segments. In one embodiment, the juxtaposedrecombinase recognition sites are in opposite orientation with respectto one another. In a specific embodiment, the recombinase recognitionsites are different. In another specific embodiment, the recombinaserecognition sites are a IoxP site and a Iox511 site. In one embodiment,the selection cassette is a neomycin cassette.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a targeting armfor targeting the mouse κ locus 5′ with respect to the mouse Jκ genesegments, a selection cassette, a recombinase recognition site 3′ to theselection cassette, and a 3′ targeting arm for targeting a mouse κsequence 3′ with respect to the mouse Jκ gene segments and 5′ to themouse κ intronic enhancer. In one embodiment, the selection cassette isa hygromycin-TK cassette. In one embodiment, the recombinase recognitionsite is in the same direction with respect to transcription as theselection cassette. In a specific embodiment, the recombinaserecognition site is a IoxP site.

In one aspect, an isolated DNA construct is provided, comprising, from5′ to 3′ with respect to the direction of transcription, a first mousegenomic fragment comprising sequence 5′ of the endogenous mouse Vκ genesegments, a first recombinase recognition site, a second recombinaserecognition site, and a second mouse genomic fragment comprisingsequence 3′ of the endogenous mouse Jκ gene segments and 5′ of the mouseκ intronic enhancer.

In one aspect, a genetically modified mouse is provided, wherein thegenetic modification comprises a modification with one or more of theDNA constructs described above or herein.

In one aspect, use of an isolated DNA construct to make a mouse asdescribed herein is provided. In one aspect, use of an isolated DNAconstruct as described herein in a method for making an antigen-bindingprotein is provided.

In one aspect, a non-human stem cell is provided that comprises atargeting vector that comprises a DNA construct as described above andherein. In one aspect, a non-human stem cell is provided, wherein thenon-human stem cell is derived from a mouse described herein.

In one embodiment, the non-human stem cell is an embryonic stem (ES)cell. In a specific embodiment, the ES cell is a mouse ES cell.

In one aspect, use of a non-human stem cell as described herein to makea mouse as described herein is provided. In one aspect, use of anon-human stem cell as described herein to make an antigen-bindingprotein is provided.

In one aspect, a mouse embryo is provided, wherein the mouse embryocomprises a genetic modification as provided herein. In one embodiment,a host mouse embryo that comprises a donor ES cell is provided, whereinthe donor ES cell comprises a genetic modification as described herein.In one embodiment, the mouse embryo is a pre-morula stage embryo. In aspecific embodiment, the pre-morula stage embryo is a 4-cell stageembryo or an 8-cell stage embryo. In another specific embodiment, themouse embryo is a blastocyst.

In one aspect, use of a mouse embryo as described herein to make a mouseas described herein is provided. In one aspect, use of a mouse embryo asdescribed herein to make an antigen-binding protein is provided.

In one aspect, a non-human cell is provided, wherein the non-human cellcomprises a rearranged immunoglobulin light chain gene sequence derivedfrom a genetically modified mouse as described herein. In oneembodiment, the cell is a B cell. In one embodiment, the cell is ahybridoma. In one embodiment, the cell encodes an immunoglobulin lightchain variable domain and/or an immunoglobulin heavy chain variabledomain that is somatically mutated.

In one aspect, a non-human cell is provided, wherein the non-human cellcomprises a rearranged immunoglobulin light chain gene sequence derivedfrom a genetically modified mouse as described herein. In oneembodiment, the cell is a B cell. In one embodiment, the cell is ahybridoma. In one embodiment, the cell encodes an immunoglobulin lightchain variable domain and/or an immunoglobulin heavy chain variabledomain that is somatically mutated.

In one aspect, use of a non-human cell as described herein to make amouse as described herein is provided. In one aspect, use of a non-humancell as described herein to make an antigen-binding protein is provided.

In one aspect, a mouse B cell is provided that expresses animmunoglobulin light chain that comprises (a) a variable region derivedfrom a hVλ gene segment and a hJλ gene segment; and, (b) a mouse C_(L)gene. In one embodiment, the mouse C_(L) gene is selected from a OK anda Cλ gene. In a specific embodiment, the Cλ gene is Cλ2. In a specificembodiment, the mouse Cλ gene is derived from a Cλ gene that is at least60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least98% identical to mouse Cλ2. In one embodiment, the mouse B cell furtherexpresses a cognate heavy chain that comprises (c) a variable regionderived from a hV_(H), a hD_(H), and (d) a hJ_(H) segment. In oneembodiment, the B cell does not comprise a rearranged λ gene. In anotherembodiment, the B cell does not comprise a rearranged κ gene.

In one aspect, a method for making an antibody in a genetically modifiedmouse is provided, comprising: (a) exposing a genetically modified mouseto an antigen, wherein the mouse has a genome comprising at least onehVλ and at least one hJλ at an endogenous light chain locus, wherein theendogenous light chain locus comprises a mouse C_(L) gene; (b) allowingthe genetically modified mouse to develop an immune response to theantigen; and, (c) isolating from the mouse of (b) an antibody thatspecifically recognizes the antigen, or isolating from the mouse of (b)a cell comprising an immunoglobulin domain that specifically recognizesthe antigen, wherein the antibody comprises a light chain derived from ahVλ, a hJλ and a mouse C_(L) gene. In a specific embodiment, the mouseC_(L) gene is a mouse Cκ gene.

In one embodiment, a method for making an antibody in a geneticallymodified mouse is provided, comprising: (a) exposing a geneticallymodified mouse to an antigen, wherein the mouse has a genome comprisingat least one hVλ at an endogenous κ locus and at least one hJλ at the κlocus, wherein the κ locus comprises a mouse Cκ gene; (b) allowing thegenetically modified mouse to develop an immune response to the antigen;and, (c) isolating from the mouse of (b) an antibody that specificallyrecognizes the antigen, or isolating from the mouse of (b) a cellcomprising an immunoglobulin domain that specifically recognizes theantigen, wherein the antibody comprises a light chain derived from ahVλ, a hJλ and a mouse Cκ gene.

In one embodiment, the κ light chain constant gene is selected from ahuman Cκ gene and a mouse Cκ gene.

In one embodiment, a method for making an antibody in a geneticallymodified mouse is provided, comprising: (a) exposing a geneticallymodified mouse to an antigen, wherein the mouse has a genome comprisingat least one hVλ at a λ light chain locus and at least one Jλ at the λlight chain locus, wherein the λ light chain locus comprises a mouse Cλgene; (b) allowing the genetically modified mouse to develop an immuneresponse to the antigen; and, (c) isolating from the mouse of (b) anantibody that specifically recognizes the antigen, or isolating from themouse of (b) a cell comprising an immunoglobulin domain thatspecifically recognizes the antigen, or identifying in the mouse of B anucleic acid sequence encoding a heavy and/or light chain variabledomain that binds the antigen, wherein the antibody comprises a lightchain derived from a hVλ, a hJλ and a mouse Cλ gene.

In one embodiment, the λ light chain constant gene is selected from ahuman Cλ gene and a mouse Cλ gene. In one embodiment, the λ light chainconstant gene is a human Cλ gene. In a specific embodiment, the human Cλgene is selected from Cλ1, Cλ2, Cλ3 and Cλ7. In one embodiment, the λlight chain constant gene is a mouse Cλ gene. In a specific embodiment,the mouse Cλ gene is selected from Cλ1, Cλ2 and Cλ3. In a more specificembodiment, the mouse Cλ gene is Cλ2. In another specific embodiment,the mouse Cλ gene is derived from a Cλ gene that is at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%, or at least 98%identical to mouse Cλ2.

In one aspect, a method for making a rearranged antibody gene in agenetically modified mouse is provided, comprising: (a) exposing agenetically modified mouse to an antigen, wherein the geneticmodification comprises a hVλ and a hJλ at an endogenous light chainlocus, wherein the endogenous light chain locus comprises a mouse C_(L)gene or functional fragment thereof; and, (b) identifying a rearrangedimmunoglobulin gene in said mouse, wherein the rearranged immunoglobulingene comprises a λ light chain variable region gene segment and a C_(L)gene or functional fragment thereof.

In one embodiment, the method further comprises cloning a nucleic acidsequence encoding a heavy and/or light chain variable region from themouse, wherein the heavy and/or light chain variable region is from anantibody that comprises a human Vλ and a mouse C_(L).

In one embodiment, the mouse C_(L) gene or functional fragment thereofis selected from a human C_(L) gene and a mouse C_(L) gene, orfunctional fragment thereof.

In one embodiment, a method for making a rearranged antibody gene in agenetically modified mouse is provided, comprising: (a) exposing agenetically modified mouse to an antigen, wherein the geneticmodification comprises a hVλ and a hJλ at a κ light chain locus, whereinthe κ light chain locus comprises a mouse C| gene or functional fragmentthereof; and, (b) identifying a rearranged immunoglobulin gene in saidmouse, wherein the rearranged immunoglobulin gene comprises a λ lightchain variable region gene segment and a C| gene or functional fragmentthereof.

In one embodiment, the κ light chain constant gene or functionalfragment thereof is selected from a human Cκ gene and a mouse Cκ gene,or a functional fragment thereof.

In one embodiment, the method further comprises cloning a nucleic acidsequence encoding a heavy and/or light chain variable region from themouse, wherein the heavy and/or light chain variable region is from anantibody that comprises a human Vλ and a mouse Cκ.

In one embodiment, a method for making a rearranged antibody gene in agenetically modified mouse is provided, comprising: (a) exposing agenetically modified mouse to an antigen, wherein the geneticmodification comprises a hVλ and a hJλ at a mouse λ light chain locus,wherein the λ light chain locus comprises a mouse Cλ gene or functionalfragment thereof; and, (b) identifying a rearranged immunoglobulin genein said mouse, wherein the rearranged immunoglobulin gene comprises a λlight chain variable region gene segment and a C└ gene or functionalfragment thereof.

In one embodiment, the λ light chain constant gene or functionalfragment thereof is selected from a human Cλ gene and a mouse Cλ gene,or a functional fragment thereof. In a specific embodiment, the λ lightchain constant gene is a mouse Cλ gene, or a functional fragmentthereof.

In one embodiment, the method further comprises cloning a nucleic acidsequence encoding a heavy and/or light chain variable region from themouse, wherein the heavy and/or light chain variable region is from anantibody that comprises a human Vλ and a mouse Cλ.

In one aspect, a method for making an antibody is provided, comprisingexposing a mouse as described herein to an antigen, allowing the mouseto mount an immune response that comprises making an antibody thatspecifically binds the antigen, identifying a rearranged nucleic acidsequence in the mouse that encodes heavy chain and a rearranged nucleicacid sequence in the mouse that encodes a cognate light chain variabledomain sequence of an antibody, wherein the antibody specifically bindsthe antigen, and employing the nucleic acid sequences of the heavy andlight chain variable domains fused to human constant domains to make adesired antibody, wherein the desired antibody comprises a light chainthat comprises a Vλ domain fused to a C_(L) domain. In one embodiment,the Vλ domain is human and the C_(L) domain is a human or mouse Cλdomain. In one embodiment, the Vλ domain is mouse and the C_(L) domainis a human or mouse Cκ domain.

In one embodiment, a method for making an antibody is provided,comprising exposing a mouse as described herein to an antigen, allowingthe mouse to mount an immune response that comprises making an antibodythat specifically binds the antigen, identifying a rearranged nucleicacid sequence in the mouse that encodes a heavy chain and a rearrangednucleic acid sequence in the mouse that encodes a cognate light chainvariable domain sequence of an antibody, wherein the antibodyspecifically binds the antigen, and employing the nucleic acid sequencesof the heavy and light chain variable domains fused to nucleic acidsequences of human constant domains to make a desired antibody, whereinthe desired antibody comprises a light chain that comprises a Vλ domainfused to a Cκ domain.

In one embodiment, a method for making an antibody is provided,comprising exposing a mouse as described herein to an antigen, allowingthe mouse to mount an immune response that comprises making an antibodythat specifically binds the antigen, identifying a rearranged nucleicacid sequence in the mouse that encodes a heavy chain variable domainand a rearranged nucleic acid sequence that encodes a cognate lightchain variable domain sequence of an antibody, wherein the antibodyspecifically binds the antigen, and employing the nucleic acid sequencesfused to nucleic acid sequences that encode a human heavy chain constantdomain and a human light chain constant domain to make an antibodyderived from human sequences, wherein the antibody that specificallybinds the antigen comprises a light chain that comprises a human Vλdomain fused to a mouse Cλ region.

In one embodiment, the mouse Cλ region is selected from Cλ1, Cλ2 andCλ3. In a specific embodiment, the mouse Cλ region is Cλ2.

In one aspect, a method for making a rearranged antibody light chainvariable region gene sequence is provided, comprising (a) exposing amouse as described herein to an antigen; (b) allowing the mouse to mountan immune response; (c) identifying a cell in the mouse that comprises anucleic acid sequence that encodes a rearranged human Vλ domain sequencefused with a mouse C_(L) domain, wherein the cell also encodes a cognateheavy chain comprising a human V_(H) domain and a mouse C_(H) domain,and wherein the cell expresses an antibody that binds the antigen; (d)cloning from the cell a nucleic acid sequence encoding the human Vλdomain and a nucleic acid sequence encoding the cognate human V_(H)domain; and, (e) using the cloned nucleic acid sequence encoding thehuman Vλ domain and the cloned nucleic acid sequence encoding thecognate human V_(H) domain to make a fully human antibody.

In one embodiment, a method for making a rearranged antibody light chainvariable region gene sequence is provided, comprising (a) exposing amouse as described in this disclosure to an antigen; (b) allowing themouse to mount an immune response; (c) identifying a cell in the mousethat comprises a nucleic acid sequence that encodes a rearranged humanVλ domain sequence contiguous on the same nucleic acid molecule with anucleic acid sequence encoding a mouse OK domain, wherein the cell alsoencodes a cognate heavy chain comprising a human V_(H) domain and amouse C_(H) domain, and wherein the cell expresses an antibody thatbinds the antigen; (d) cloning from the cell a nucleic acids sequenceencoding the human Vλ domain and a nucleic acid sequence encoding thecognate human V_(H) domain; and, (e) using the cloned nucleic acidsequence encoding the human Vλ domain and the cloned nucleic acidsequence encoding the cognate human V_(H) domain to make a fully humanantibody.

In one embodiment, a method for making a rearranged antibody light chainvariable region gene sequence is provided, comprising (a) exposing amouse as described herein to an antigen; (b) allowing the mouse to mountan immune response to the antigen; (c) identifying a cell in the mousethat comprises DNA that encodes a rearranged human Vλ domain sequencefused with a mouse Cλ domain, wherein the cell also encodes a cognateheavy chain comprising a human V_(H) domain and a mouse C_(H) domain,and wherein the cell expresses an antibody that binds the antigen; (d)cloning from the cell a nucleic acid sequence encoding the rearrangedhuman Vλ domain and a nucleic acid sequence encoding the cognate humanV_(H) domain; and, (e) using the cloned nucleic acid sequence encodingthe human Vλ domain and the cloned nucleic acid sequence encoding thecognate human V_(H) domain to make a fully human antibody. In oneembodiment, the mouse Cλ domain is mouse Cλ2. In a specific embodiment,the mouse Cλ domain is derived from a Cλ gene that is at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%, or at least 98%identical to mouse Cλ2.

In one aspect, a genetically modified mouse is provided that expresses ahuman λ-derived light chain fused to an endogenous light chain constantregion (C_(L)), wherein the mouse, upon immunization with antigen, makesan antibody comprising a human Vλ domain fused to a mouse C_(L) domain.In one embodiment, the mouse C_(L) domain is selected from a Cκ domainand a Cλ domain. In one embodiment, the mouse C_(L) domain is a Cκdomain. In one embodiment, the mouse C_(L) domain is a Cλ domain. In aspecific embodiment, the Cλ domain is Cλ2. In a specific embodiment, themouse Cλ domain is derived from a Cλ gene that is at least 60%, at least70%, at least 80%, at least 90%, at least 95%, or at least 98% identicalto mouse Cλ2.

In one aspect, a genetically modified mouse comprising a modifiedendogenous κ or λ light chain locus as described herein, is providedthat expresses a plurality of immunoglobulin λ light chains associatedwith a plurality of immunoglobulin heavy chains. In one embodiment, theheavy chain comprises a human sequence. In various embodiments, thehuman sequence is selected from a variable sequence, a C_(H)1, a hinge,a C_(H)2, a C_(H)3, and a combination thereof. In one embodiment, theplurality of immunoglobulin λ light chains comprises a human sequence.In various embodiments, the human sequence is selected from a variablesequence, a constant sequence, and a combination thereof. In oneembodiment, the mouse comprises a disabled endogenous immunoglobulinlocus and expresses the heavy chain and/or the λ light chain from atransgene or extrachromosomal episome. In one embodiment, the mousecomprises a replacement at an endogenous mouse locus of some or allendogenous mouse heavy chain gene segments (i.e., V, D, J), and/or someor all endogenous mouse heavy chain constant sequences (e.g., C_(H)1,hinge, C_(H)2, C_(H)3, or a combination thereof), and/or some or allendogenous mouse light chain sequences (e.g., V, J, constant, or acombination thereof), with one or more human immunoglobulin sequences.

In one aspect, a mouse suitable for making antibodies that have a humanλ-derived light chain is provided, wherein all or substantially allantibodies made in the mouse are expressed with a human λ-derived lightchain. In one embodiment, the human λ-derived light chain is expressedfrom an endogenous light chain locus. In one embodiment, the endogenouslight chain locus is a κ light chain locus. In a specific embodiment,the κ light chain locus is a mouse κ light chain locus.

In one aspect, a method for making a λ-derived light chain for a humanantibody is provided, comprising obtaining from a mouse as describedherein a light chain sequence and a heavy chain sequence, and employingthe light chain sequence and the heavy chain sequence in making a humanantibody.

In one aspect, a method for making an antigen-binding protein isprovided, comprising exposing a mouse as described herein to an antigen;allowing the mouse to mount an immune response; and obtaining from themouse an antigen-binding protein that binds the antigen, or obtainingfrom the mouse a sequence to be employed in making an antigen-bindingprotein that binds the antigen.

In one aspect, a cell derived from a mouse as described herein isprovided. In one embodiment, the cell is selected from an embryonic stemcell, a pluripotent cell, an induced pluripotent cell, a B cell, and ahybridoma.

In one aspect, a cell is provided that comprises a genetic modificationas described herein. In one embodiment, the cell is a mouse cell. In oneembodiment, the cell is selected from a hybridoma and a quadroma. In oneembodiment, the cell expresses an immunoglobulin light chain thatcomprises a human λ variable sequence fused with a mouse constantsequence. In a specific embodiment, the mouse constant sequence is amouse κ constant sequence.

In one aspect, a tissue derived from a mouse as described herein isprovided.

In one aspect, use of a mouse or a cell as described herein to make anantigen-binding protein is provided. In one embodiment, theantigen-binding protein is a human protein. In one embodiment, the humanprotein is a human antibody.

In one aspect, an antigen-binding protein made by a mouse, cell, tissue,or method as described herein is provided. In one embodiment, theantigen-binding protein is a human protein. In one embodiment, the humanprotein is a human antibody.

Any of the embodiments and aspects described herein can be used inconjunction with one another, unless otherwise indicated or apparentfrom the context. Other embodiments will become apparent to thoseskilled in the art from a review of the ensuing description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a detailed illustration, not to scale, of the human λ lightchain locus including the clusters of Vλ gene segments (A, B and C) andthe Jλ and Cλ region pairs (J-C pairs)

FIG. 2 shows a general illustration, not to scale, of a targetingstrategy used to inactivate the endogenous mouse λ light chain locus.

FIG. 3 shows a general illustration, not to scale, of a targetingstrategy used to inactivate the endogenous mouse κ light chain locus.

FIG. 4A shows a general illustration, not to scale of an initialtargeting vector for targeting the endogenous mouse λ light chain locuswith human λ light chain sequences including 12 hVλ gene segments andhJλ1 gene segment (12/1-λ Targeting Vector).

FIG. 4B shows a general illustration, not to scale, of four initialtargeting vectors for targeting the endogenous mouse κ light chain locuswith human λ light chain sequences including 12 hVλ gene segments andhJλ1 gene segment (12/1-κ Targeting Vector), 12 hVλ gene segments andhJλ1, 2, 3 and 7 gene segments (12/4-κ Targeting Vector), 12 hVλ genesegments, a human Vκ-Jκ genomic sequence and hJλ1 gene segment (12(κ)1-κTargeting Vector) and 12 hVλ gene segments, a human Vκ-Jκ genomicsequence and hJλ1, 2, 3 and 7 gene segments (12(κ)4-κ Targeting Vector).

FIG. 5A shows a general illustration, not to scale, of a targetingstrategy for progressive insertion of 40 hVλ gene segments and a singlehJλ gene segment into the mouse λ light chain locus.

FIG. 5B shows a general illustration, not to scale, of a targetingstrategy for progressive insertion of 40 hVλ gene segments and a singlehJλ gene segment into the mouse κ locus.

FIG. 6 show a general illustration, not to scale, of the targeting andmolecular engineering steps employed to make unique human λ-κ hybridtargeting vectors for construction of a hybrid light chain locuscontaining a human κ intergenic sequence, multiple hJλ gene segments orboth.

FIG. 7A shows a general illustration, not to scale, of the locusstructure for a modified mouse λ light chain locus containing 40 hVλgene segments and a single hJλ gene segment operably linked to theendogenous Cλ2 gene.

FIG. 7B shows a general illustration, not to scale, of the locusstructure for four independent, modified mouse κ light chain locicontaining 40 hVλ gene segments and either one or four hJλ gene segmentswith or without a contiguous human Vκ-Jκ genomic sequence operablylinked to the endogenous Cκ gene.

FIG. 8A shows contour plots of Igλ⁺ and Igκ⁺ splenocytes gated on CD19⁺from a wild type mouse (WT), a mouse homozygous for 12 hVλ and four hJλgene segments including a human Vκ-Jκ genomic sequence (12hVλ-VκJκ-4hJλ)and a mouse homozygous for 40 hVλ and one hJλ gene segment (40hVλ-1hJλ).

FIG. 8B shows the total number of CD19⁺ B cells in harvested spleensfrom wild type (WT), mice homozygous for 12 hVλ and four hJλ genesegments including a human Vκ-Jκ genomic sequence (12hVλ-VκJκ-4hJλ) andmice homozygous for 40 hVλ and one hJλ gene segment (40hVλ-1hJλ).

FIG. 9A, in the top panel, shows contour plots of splenocytes gated onsinglets and stained for B and T cells (CD19⁺ and CD3⁺, respectively)from a wild type mouse (WT) and a mouse homozygous for 40 hVλ and fourJλ gene segments including a human Vκ-Jκ genomic sequence(40hVλ-VκJκ-4hJλ). The bottom panel shows contour plots of splenocytesgated on CD19⁺ and stained for Igλ⁺ and Igκ⁺ expression from a wild typemouse (WT) and a mouse homozygous for 40 hVλ and four Jλ gene segmentsincluding a human Vκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ).

FIG. 9B shows the total number of CD19⁺, CD19⁺Igκ⁺ and CD19⁺Igλ⁺ B cellsin harvested spleens from wild type mice (WT) and mice homozygous for 40hVλ and four Jλ gene segments including a human Vκ-Jκ genomic sequence(40hVλ-VκJκ-4hJλ).

FIG. 9C shows contour plots of splenocytes gated on CD19⁺ and stainedfor immunoglobulin D (IgD) and immunoglobulin M (IgM) from a wild typemouse (WT) and a mouse homozygous for 40 hVλ and four Jλ gene segmentsincluding a human Vκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ). Mature (72for WT, 51 for 40hVλ-VκJκ-4hJλ) and transitional (13 for WT, 22 for40hVλ-VκJκ-4hJλ) B cells are noted on each of the contour plots.

FIG. 9D shows the total number of CD19⁺ B cells, transitional B cells(CD19⁺IgM^(hi)IgD^(lo)) and mature B cells (CD19⁺IgM^(lo)IgD^(hi)) inharvested spleens from wild type mice (WT) and mice homozygous for 40hVλ and four Jλ gene segments including a human Vκ-Jκ genomic sequence(40hVλ-VκJκ-4hJλ).

FIG. 10A, in the top panel, shows contour plots of bone marrow stainedfor B and T cells (CD19⁺ and CD3⁺, respectively) from a wild type mouse(WT) and a mouse homozygous for 40 hVλ and four Jλ gene segmentsincluding a human Vκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ). The bottompanel shows contour plots of bone marrow gated on CD19⁺ and stained forckit⁺ and CD43⁺ from a wild type mouse (WT) and a mouse homozygous for40 hVλ and four Jλ gene segments including a human Vκ-Jκ genomicsequence (40hVλ-VκJκ-4hJλ). Pro and Pre B cells are noted on the contourplots of the bottom panel.

FIG. 10B shows the number of Pro (CD19⁺CD43⁺ckit⁺) and Pre(CD19⁺CD43⁻ckit⁻) B cells in bone marrow harvested from the femurs ofwild type mice (WT) and mice homozygous for 40 hVλ and four Jλ genesegments including a human Vκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ).

FIG. 10C shows contour plots of bone marrow gated on singlets stainedfor immunoglobulin M (IgM) and B220 from a wild type mouse (WT) and amouse homozygous for 40 hVλ and four Jλ gene segments including a humanVκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ). Immature, mature and pro/pre Bcells are noted on each of the contour plots.

FIG. 10D shows the total number of immature (B220^(int)IgM⁺) and mature(B220^(hi)IgM⁺) B cells in bone marrow isolated from the femurs of wildtype mice (WT) and mice homozygous for 40 hVλ and four Jλ gene segmentsincluding a human Vκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ).

FIG. 10E shows contour plots of bone marrow gated on immature(B220^(int)IgM⁺) and mature (B220^(hi)IgM⁺) B cells stained for Igλ andIgκ expression isolated from the femurs of a wild type mouse (WT) and amouse homozygous for 40 hVλ and four Jλ gene segments including a humanVκ-Jκ genomic sequence (40hVλ-VκJκ-4hJλ).

FIG. 11 shows a nucleotide sequence alignment of the Vλ-Jλ-Cκ junctionof eighteen independent RT-PCR clones amplified from splenocyte RNA ofmice bearing human λ light chain gene sequences at an endogenous mouse κlight chain locus. A6=SEQ ID NO:57; B6=SEQ ID NO:58; F6=SEQ ID NO:59;B7=SEQ ID NO:60; E7=SEQ ID NO:61; F7=SEQ ID NO:62; C8=SEQ ID NO:63;E12=SEQ ID NO:64; 1-4=SEQ ID NO:65; 1-20=SEQ ID NO:66; 3B43=SEQ IDNO:67; 5-8=SEQ ID NO:68; 5-19=SEQ ID NO:69; 1010=SEQ ID NO:70; 11A1=SEQID NO:71; 7A8=SEQ ID NO:72; 3A3=SEQ ID NO:73; 2-7=SEQ ID NO:74. Lowercase bases indicate non-germline bases resulting from either mutationand/or N addition during recombination. Consensus amino acids within theFramework 4 region (FWR4) encoded by the nucleotide sequence of hJλ1 andmouse Cκ are noted at the bottom of the sequence alignment.

FIG. 12 shows a nucleotide sequence alignment of the Vλ-Jλ-Cκ junctionof twelve independent RT-PCR clones amplified from splenocyte RNA ofmice bearing human λ light chain gene sequences including a contiguoushuman Vκ-Jκ genomic sequence at an endogenous mouse κ light chain locus.5-2=SEQ ID NO:87; 2-5=SEQ ID NO:88; 1-3=SEQ ID NO:89; 4B-1=SEQ ID NO:90;3B-5=SEQ ID NO:91; 7A-1=SEQ ID NO:92; 5-1=SEQ ID NO:93; 4A-1=SEQ IDNO:94; 11A-1=SEQ ID NO:95; 5-7=SEQ ID NO:96; 5-4=SEQ ID NO:97; 2-3=SEQID NO:98. Lower case bases indicate non-germline bases resulting fromeither mutation and/or N addition during recombination. Consensus aminoacids within the Framework 4 region (FWR4) encoded by the nucleotidesequence of each human Jλ and mouse Cκ are noted at the bottom of thesequence alignment.

FIG. 13 shows a nucleotide sequence alignment of the Vλ-Jλ-Cλ junctionof three independent RT-PCR clones amplified from splenocyte RNA of micebearing human λ light chain gene sequences at an endogenous mouse λlight chain locus. 2D1=SEQ ID NO:101; 2D9=SEQ ID NO:102; 3E15=SEQ IDNO:103. Lower case bases indicate non-germline bases resulting fromeither mutation and/or N addition during recombination. Consensus aminoacids within the Framework 4 region (FWR4) encoded by the nucleotidesequence of hJλ1 and mouse Cλ2 are noted at the bottom of the sequencealignment.

DETAILED DESCRIPTION

Although specific features of various embodiments are discussed indetail, the descriptions of the specific aspects, embodiments, andexamples do not limit the subject matter of the claims; it is the claimsthat describe the scope of the invention. All terms and phrases used inthis disclosure include the meanings normally ascribed to them in theart.

The term “contiguous” includes reference to occurrence on the samenucleic acid molecule, e.g., two nucleic acid sequences are “contiguous”if they occur on the same nucleic molecule but are interrupted byanother nucleic acid sequence. For example, a rearranged V(D)J sequenceis “contiguous” with a constant region gene sequence, although the finalcodon of the V(D)J sequence is not followed immediately by the firstcodon of the constant region sequence. In another example, two V genesegment sequences are “contiguous” if they occur on the same genomicfragment, although they may be separated by sequence that does notencode a codon of the V region, e.g., they may be separated by aregulatory sequence, e.g., a promoter or other noncoding sequence. Inone embodiment, a contiguous sequence includes a genomic fragment thatcontains genomic sequences arranged as found in a wild-type genome.

The phrase “derived from” when used concerning a variable region“derived from” a cited gene or gene segment includes the ability totrace the sequence back to a particular unrearranged gene segment orgene segments that were rearranged to form a gene that expresses thevariable domain (accounting for, where applicable, splice differencesand somatic mutations).

The phrase “functional” when used concerning a variable region genesegment or joining gene segment refers to usage in an expressed antibodyrepertoire; e.g., in humans Vλ gene segments 3-1, 4-3, 2-8, etc. arefunctional, whereas Vλ gene segments 3-2, 3-4, 2-5, etc. arenonfunctional.

A “heavy chain locus” includes a location on a chromosome, e.g., a mousechromosome, wherein in a wild-type mouse heavy chain variable (V_(H)),heavy chain diversity (D_(H)), heavy chain joining (J_(H)), and heavychain constant (C_(H)) region DNA sequences are found.

A “κ locus” includes a location on a chromosome, e.g., a mousechromosome, wherein in a wild-type mouse κ variable (Vκ), κ joining(Jκ), and κ constant (Cκ) region DNA sequences are found.

A “λ locus” includes a location on a chromosome, e.g., a mousechromosome, wherein in a wild-type mouse λ variable (Vλ), λ joining(Jλ), and λ constant (Cλ) region DNA sequences are found.

The term “unrearranged” includes the state of an immunoglobulin locuswherein V gene segments and J gene segments (for heavy chains, D genesegments as well) are maintained separately but are capable of beingjoined to form a rearranged V(D)J gene that comprises a single V(D), Jof the V(D)J repertoire.

Mice Expressing Human λ Variable Domains

Mice that express antibodies that are fully human, or partly human andpartly mouse, have previously been reported. VELOCIMMUNE® geneticallyengineered mice comprise a replacement of unrearranged V(D)J genesegments at endogenous mouse loci with human V(D)J gene segments.VELOCIMMUNE® mice express chimeric antibodies having human variabledomains and mouse constant domains (see, e.g., U.S. Pat. No. 7,605,237).Most other reports concern mice that express fully human antibodies fromfully human transgenes in mice that have disabled endogenousimmunoglobulin loci.

Antibody light chains are encoded by one of two separate loci: kappa (κ)and lambda (λ). Mouse antibody light chains are primarily of the κ type.Mice that make mouse antibodies, and modified mice that make fully humanor chimeric human-mouse antibodies, display a bias in light chain usage.Humans also exhibit light chain bias, but not so pronounced as in mice;the ratio of κ light chains to λ light chains in mice is about 95:5,whereas in humans the ratio is about 60:40. The more pronounced bias inmice is not thought to severely affect antibody diversity, because inmice the λ variable locus is not so diverse in the first instance. Thisis not so in humans. The human λ light chain locus is richly diverse.

The human λ light chain locus extends over 1,000 kb and contains over 80genes that encode variable (V) or joining (J) segments (FIG. 1). Withinthe human λ light chain locus, over half of all observed Vλ domains areencoded by the gene segments 1-40, 1-44, 2-8, 2-14, and 3-21. Overall,about 30 or so of the human Vλ gene segments are believed to befunctional. There are seven Jλ gene segments, only four of which areregarded as generally functional Jλ gene segments—Jλ1, Jλ2, Jλ3, andJλ7.

The λ light chain locus in humans is similar in structure to the| locusof both mice and humans in that the human λ light chain locus hasseveral variable region gene segments that are capable of recombining toform a functional light chain protein. The human λ light chain locuscontains approximately 70 V gene segments and 7 Jλ-Cλ gene segmentpairs. Only four of these Jλ-Cλ gene segment pairs appear to befunctional. In some alleles, a fifth Jλ-Cλ gene segment pair isreportedly a pseudo gene (Cλ6). The 70 Vλ gene segments appear tocontain 38 functional gene segments. The 70 Vλ sequences are arranged inthree clusters, all of which contain different members of distinct Vgene family groups (clusters A, B and C; FIG. 1). This is a potentiallyrich source of relatively untapped diversity for generating antibodieswith human V regions in non-human animals.

In stark contrast, the mouse λ light chain locus contains only two orthree (depending on the strain) mouse Vλ region gene segments (FIG. 2).At least for this reason, the severe κ bias in mice is not thought to beparticularly detrimental to total antibody diversity.

According published maps of the mouse λ light chain locus, the locusconsists essentially of two clusters of gene segments within a span ofapproximately 200 kb (FIG. 2). The two clusters contain two sets of V,J, and C genes that are capable of independent rearrangement:Vλ2-Jλ2-Cλ2-Jλ4-Cλ4 and Vλ1-Jλ3-Cλ3-Jλ1-Cλ1. Although Vλ2 has been foundto recombine with all Jλ gene segments, Vλ1 appears to exclusivelyrecombine with Cλ1. Cλ4 is believed to be a pseudo gene with defectivesplice sites.

The mouse κ light chain locus is strikingly different. The structure andnumber of gene segments that participate in the recombination eventsleading to a functional light chain protein from the mouse κ locus ismuch more complex (FIG. 3). Thus, mouse λ light chains do not greatlycontribute to the diversity of an antibody population in a typicalmouse.

Exploiting the rich diversity of the human λ light chain locus in micewould likely result in, among other things, a source for a more completehuman repertoire of light chain V domains. Previous attempts to tap thisdiversity used human transgenes containing chunks of the human λ lightchain locus randomly incorporated into the mouse genome (see, e.g., U.S.Pat. No. 6,998,514 and U.S. Pat. No. 7,435,871). Mice containing theserandomly integrated transgenes reportedly express fully human λ lightchains, however, in some cases, one or both endogenous light chain lociremain intact. This situation is not desirable as the human λ lightchain sequences contend with the mouse light chain (κ or λ) in theexpressed antibody repertoire of the mouse.

In contrast, the inventors describe genetically modified mice that arecapable of expressing one or more λ light chain nucleic acid sequencesdirectly from a mouse light chain locus, including by replacement at anendogenous mouse light chain locus. Genetically modified mice capable ofexpressing human λ light chain sequences from an endogenous locus may befurther bred to mice that comprise a human heavy chain locus and thus beused to express antibodies comprising V regions (heavy and light) thatare fully human. In various embodiments. The V regions express withmouse constant regions. In various embodiments, no endogenous mouseimmunoglobulin gene segments are present and the V regions express withhuman constant regions. These antibodies would prove useful in numerousapplications, both diagnostic as well as therapeutic.

Many advantages can be realized for various embodiments of expressingbinding proteins derived from human Vλ and Jλ gene segments in mice.Advantages can be realized by placing human λ sequences at an endogenouslight chain locus, for example, the mouse κ or λ locus. Antibodies madefrom such mice can have light chains that comprise human Vλ domainsfused to a mouse C_(L) region, specifically a mouse Cκ or Cλ region. Themice will also express human Vλ domains that are suitable foridentification and cloning for use with human C_(L) regions,specifically Cκ and/or Cλ regions. Because B cell development in suchmice is otherwise normal, it is possible to generate compatible Vλdomains (including somatically mutated Vλ domains) in the context ofeither Cλ or Cκ regions.

Genetically modified mice are described that comprise an unrearranged Vλgene segment at an immunoglobulin κ or λ light chain locus. Mice thatexpress antibodies that comprise a light chain having a human Vλ domainfused to a Cκ and/or Cλ region are described.

Sterile Transcripts of the Immunoglobulin κ Light Chain Locus

Variations on the theme of expressing human immunoglobulin λ sequencesin mice are reflected in various embodiments of genetically modifiedmice capable of such expression. Thus, in some embodiments, thegenetically modified mice comprise certain non-coding sequence(s) from ahuman locus. In one embodiment, the genetically modified mouse compriseshuman Vλ and Jλ gene segments at an endogenous κ light chain locus, andfurther comprises a human κ light chain genomic fragment. In a specificembodiment, the human κ light chain genomic fragment is a non-codingsequence naturally found between a human Vκ gene segment and a human Jκgene segment.

The human and mouse κ light chain loci contain sequences that encodesterile transcripts that lack either a start codon or an open readingframe, and that are regarded as elements that regulate transcription ofthe κ light chain loci. These sterile transcripts arise from anintergenic sequence located downstream or 3′ of the most proximal Vκgene segment and upstream or 5′ of the κ light chain intronic enhancer(Eκi) that is upstream of the κ light chain constant region gene (Cκ).The sterile transcripts arise from rearrangement of the intergenicsequence to form a VκJκ1 segment fused to a Cκ.

A replacement of the κ light chain locus upstream of the Cκ gene wouldremove the intergenic region encoding the sterile transcripts.Therefore, in various embodiments, a replacement of mouse κ light chainsequence upstream of the mouse Cκ gene with human λ light chain genesegments would result in a humanized mouse κ light chain locus thatcontains human Vλ and Jλ gene segments but not the κ light chainintergenic region that encodes the sterile transcripts.

As described herein, humanization of the endogenous mouse κ light chainlocus with human λ light chain gene segments, wherein the humanizationremoves the intergenic region, results in a striking drop in usage ofthe κ light chain locus, coupled with a marked increase in λ light chainusage. Therefore, although a humanized mouse that lacks the intergenicregion is useful in that it can make antibodies with human light chainvariable domains (e.g., human λ or K domains), usage from the locusdecreases.

Also described is humanization of the endogenous mouse κ light chainlocus with human Vλ and Jλ gene segments coupled with an insertion of ahuman κ intergenic region to create a Vλ locus that contains, withrespect to transcription, between the final human Vλ gene segment andthe first human Jλ gene segment, a κ intergenic region; which exhibits aB cell population with a higher expression than a locus that lacks the κintergenic region. This observation is consistent with a hypothesis thatthe intergenic region—directly through a sterile transcript, orindirectly—suppresses usage from the endogenous λ light chain locus.Under such a hypothesis, including the intergenic region would result ina decrease in usage of the endogenous λ light chain locus, leaving themouse a restricted choice but to employ the modified (λ into κ) locus togenerate antibodies.

In various embodiments, a replacement of mouse κ light chain sequenceupstream of the mouse Cκ gene with human λ light chain sequence furthercomprises a human κ light chain intergenic region disposed, with respectto transcription, between the 3′ untranslated region of the 3′ most Vλgene segment and 5′ to the first human Jλ gene segment. Alternatively,such an intergenic region may be omitted from a replaced endogenous κlight chain locus (upstream of the mouse Cκ gene) by making a deletionin the endogenous λ light chain locus. Likewise, under this embodiment,the mouse generates antibodies from an endogenous κ light chain locuscontaining human λ light chain sequences.

Approaches to Engineering Mice to Express Human Vλ Domains

Various approaches to making genetically modified mice that makeantibodies that contain a light chain that has a human Vλ domain fusedto an endogenous C_(L) (e.g. Cκ or Cλ) region are described. Geneticmodifications are described that, in various embodiments, comprise adeletion of one or both endogenous light chain loci. For example, toeliminate mouse λ light chains from the endogenous antibody repertoire adeletion of a first Vλ-Jλ-Cλ gene cluster and replacement, in whole orin part, of the Vλ-Jλ gene segments of a second gene cluster with humanVλ-Jλ gene segments can be made. Genetically modified mouse embryos,cells, and targeting constructs for making the mice, mouse embryos, andcells are also provided.

The deletion of one endogenous Vλ-Jλ-Cλ gene cluster and replacement ofthe Vλ-Jλ gene segments of another endogenous Vλ-Jλ-Cλ gene clusteremploys a relatively minimal disruption in natural antibody constantregion association and function in the animal, in various embodiments,because endogenous Cλ genes are left intact and therefore retain normalfunctionality and capability to associate with the constant region of anendogenous heavy chain. Thus, in such embodiments the modification doesnot affect other endogenous heavy chain constant regions dependent uponfunctional light chain constant regions for assembly of a functionalantibody molecule containing two heavy chains and two light chains.Further, in various embodiments the modification does not affect theassembly of a functional membrane-bound antibody molecule involving anendogenous heavy chain and a light chain, e.g., a hV└ domain linked to amouse Cλ region. Because at least one functional Cλ gene is retained atthe endogenous locus, animals containing a replacement of the Vλ-Jλ genesegments of an endogenous Vλ-Jλ-Cλ gene cluster with human Vλ-Jλ genesegments should be able to make normal λ light chains that are capableof binding antigen during an immune response through the human Vλ-Jλgene segments present in the expressed antibody repertoire of theanimal.

A schematic illustration (not to scale) of a deleted endogenous mouseVλ-Jλ-Cλ gene cluster is provided in FIG. 2. As illustrated, the mouse λlight chain locus is organized into two gene clusters, both of whichcontain function gene segments capable of recombining to form a functionmouse λ light chain. The endogenous mouse Vλ1-Jλ3-Cλ3-Jλ1-Cλ1 genecluster is deleted by a targeting construct (Targeting Vector 1) with aneomycin cassette flanked by recombination sites. The other endogenousgene cluster (Vλ2-Vλ3-Jλ2-Cλ2-Jλ4-Cλ4) is deleted in part by a targetingconstruct (Targeting Vector 2) with a hygromycin-thymidine kinasecassette flanked by recombination sites. In this second targeting event,the Cλ2-Jλ4-Cλ4 endogenous gene segments are retained. The secondtargeting construct (Targeting Vector 2) is constructed usingrecombination sites that are different than those in the first targetingconstruct (Targeting Vector 1) thereby allowing for the selectivedeletion of the selection cassette after a successful targeting has beenachieved. The resulting double-targeted locus is functionally silencedin that no endogenous λ light chain can be produced. This modified locuscan be used for the insertion of human Vλ and Jλ gene segments to createan endogenous mouse λ locus comprising human Vλ and Jλ gene segments,whereby, upon recombination at the modified locus, the animal produces λlight chains comprising rearranged human Vλ and Jλ gene segments linkedto an endogenous mouse Cλ gene segment.

Genetically modifying a mouse to render endogenous λ gene segmentsnonfunctional, in various embodiments, results in a mouse that exhibitsexclusively κ light chains in its antibody repertoire, making the mouseuseful for evaluating the role of λ light chains in the immune response,and useful for making an antibody repertoire comprising Vκ domains butnot Vλ domains.

A genetically modified mouse that expresses a hVλ linked to a mouse Cλgene having been recombined at the endogenous mouse λ light chain locuscan be made by any method known in the art. A schematic illustration(not to scale) of the replacement of the endogenous mouse Vλ2-Vλ3-Jλ2gene segments with human Vλ and Jλ gene segments is provided in FIG. 4A.As illustrated, an endogenous mouse λ light chain locus that had beenrendered nonfunctional is replaced by a targeting construct (12/1-λTargeting Vector) that includes a neomycin cassette flanked byrecombination sites. The Vλ2-Vλ3-Jλ2 gene segments are replaced with agenomic fragment containing human λ sequence that includes 12 hVλ genesegments and a single hJλ gene segment.

Thus, this first approach positions one or more hVλ gene segments at theendogenous λ light chain locus contiguous with a single hJλ gene segment(FIG. 4A).

Further modifications to the modified endogenous λ light chain locus canbe achieved with using similar techniques to insert more hVλ genesegments. For example, schematic illustrations of two additionaltargeting constructs (+16-λ and +12-λ Targeting Vectors) used forprogressive insertion of addition human hVλ gene segments are providedin FIG. 5A. As illustrated, additional genomic fragments containingspecific human hVλ gene segments are inserted into the modifiedendogenous λ light chain locus in successive steps using homologyprovided by the previous insertion of human λ light chain sequences.Upon recombination with each targeting construct illustrated, insequential fashion, 28 additional hVλ gene segments are inserted intothe modified endogenous λ light chain locus. This creates a chimericlocus that produces a λ light chain protein that comprises human Vλ-Jλgene segments linked to a mouse Cλ gene.

The above approaches to insert human λ light chain gene segments at themouse λ locus, maintains the enhancers positioned downstream of theCλ2-Jλ4-Cλ4 gene segments (designated Enh 2.4, Enh and Enh 3.1 FIG. 4Aand FIG. 5A). This approach results in a single modified allele at theendogenous mouse λ light chain locus (FIG. 7A).

Compositions and methods for making a mouse that expresses a light chaincomprising hVλ and Jλ gene segments operably linked to a mouse Cλ genesegment, are provided, including compositions and method for making amouse that expresses such genes from an endogenous mouse λ light chainlocus. The methods include selectively rendering one endogenous mouseVλ-Jλ-Cλ gene cluster nonfunctional (e.g., by a targeted deletion), andemploying a hVλ and Jλ gene segments at the endogenous mouse λ lightchain locus to express a hVλ domain in a mouse.

Alternatively, in a second approach, human λ light chain gene segmentsmay be positioned at the endogenous κ light chain locus. The geneticmodification, in various embodiments, comprises a deletion of theendogenous κ light chain locus. For example, to eliminate mouse κ lightchains from the endogenous antibody repertoire a deletion of the mouseVκ and Jκ gene segments can be made. Genetically modified mouse embryos,cells, and targeting constructs for making the mice, mouse embryos, andcells are also provided.

For the reasons stated above, the deletion of the mouse Vκ and Jκ genesegments employs a relatively minimal disruption. A schematicillustration (not to scale) of deleted mouse Vκ and Jκ gene segments isprovided in FIG. 3. The endogenous mouse Vκ and Jκ gene segments aredeleted via recombinase-mediated deletion of mouse sequences positionbetween two precisely positioned targeting vectors each employingsite-specific recombination sites. A first targeting vector (JκTargeting Vector) is employed in a first targeting event to delete themouse Jκ gene segments. A second targeting vector (Vκ Targeting Vector)is employed in a second, sequential targeting event to delete a sequencelocated 5′ of the most distal mouse Vκ gene segment. Both targetingvectors contain site-specific recombination sites thereby allowing forthe selective deletion of both selection cassettes and all interveningmouse κ light chain sequences after a successful targeting has beenachieved. The resulting deleted locus is functionally silenced in thatno endogenous κ light chain can be produced. This modified locus can beused for the insertion of hVλ and Jλ gene segments to create anendogenous mouse κ locus comprising hVλ and Jλ gene segments, whereby,upon recombination at the modified locus, the animal produces λ lightchains comprising rearranged hVλ and Jλ gene segments operably linked toan endogenous mouse OK gene segment. Various targeting vectorscomprising human λ light chain sequences can be used in conjunction withthis deleted mouse κ locus to create a hybrid light chain locuscontaining human λ gene segments operably linked with a mouse OK region.

Thus, a second approach positions one or more human Vλ gene segments arepositioned at the mouse κ light chain locus contiguous with a singlehuman Jλ gene segment (12/1-κ Targeting Vector, FIG. 4B).

In various embodiments, modifications to this approach can be made toadd gene segments and/or regulatory sequences to optimize the usage ofthe human λ light chain sequences from the mouse κ locus within themouse antibody repertoire.

In a third approach, one or more hVλ gene segments are positioned at themouse κ light chain locus contiguous with four hJλ gene sequences(12/4-κ Targeting Vector FIG. 4B).

In a third approach, one or more hVλ gene segments are positioned at themouse κ light chain locus contiguous with a human κ intergenic sequenceand a single hJλ gene sequence (12(κ)1-κ Targeting Vector, FIG. 4B).

In a fourth approach, one or more hVλ gene segments are positioned atthe mouse κ light chain locus contiguous with a human κ intergenicsequence four hJλ gene sequences (12(κ)4-κ Targeting Vector FIG. 4B).

All of the above approaches to insert human λ light chain gene segmentsat the mouse κ locus, maintain the κ intronic enhancer element upstreamof the Cκ gene (designated Eκi, FIG. 4B and FIG. 5B) and the 3′ κenhancer downstream of the Cκ gene (designated Eκ3′, FIG. 4B and FIG.5B). The approaches result in four separate modified alleles at theendogenous mouse κ light chain locus (FIG. 7B).

In various embodiments, genetically modified mouse comprise a knockoutof the endogenous mouse λ light chain locus. In one embodiment, the λlight chain locus is knocked out by a strategy that deletes the regionspanning Vλ2 to Jλ2, and the region spanning Vλ1 to Cλ1 (FIG. 2). Anystrategy that reduces or eliminates the ability of the endogenous λlight chain locus to express endogenous λ domains is suitable for usewith embodiments in this disclosure.

Lambda Domain Antibodies from Genetically Modified Mice

Mice comprising human λ sequences at either the mouse κ or λ light chainlocus will express a light chain that comprises a hVλ region fused to amouse C_(L) (Cκ or Cλ) region. These are advantageously bred to micethat (a) comprise a functionally silenced light chain locus (e.g., aknockout of the endogenous mouse κ or λ light chain locus); (b) comprisean endogenous mouse └ light chain locus that comprises hV and hJ genesegments operably linked to an endogenous mouse Cλ gene; (c) comprise anendogenous mouse κ light chain locus that comprises hVκ and hJκ genesegments operably linked to an endogenous mouse Cκ gene; and, (d) amouse in which one κ allele comprises hVκs and hJκs; the other κ allelecomprising hVλs and hJλs; one λ allele comprising hVλs and hJλs and oneλ allele silenced or knocked out, or both λ alleles comprising hVλs andhJλs; and, two heavy chain alleles that each comprise hV_(H)s, hD_(H)s,and hJ_(H)s.

The antibodies that comprise the hVλ domains expressed in the context ofeither Cκ or Cλ are used to make fully human antibodies by cloning thenucleic acids encoding the hVλ domains into expression constructs thatbear genes encoding human Cλ. Resulting expression constructs aretransfected into suitable host cells for expressing antibodies thatdisplay a fully hVλ domain fused to hCλ.

EXAMPLES

The following examples are provided so as to describe how to make anduse methods and compositions of the invention, and are not intended tolimit the scope of what the inventors regard as their invention. Unlessindicated otherwise, temperature is indicated in Celsius, and pressureis at or near atmospheric.

Example I Deletion of the Mouse Immunoglobulin Light Chain Loci

Various targeting constructs were made using VELOCIGENE® technology(see, e.g., U.S. Pat. No. 6,586,251 and Valenzuela et al. (2003)High-throughput engineering of the mouse genome coupled withhigh-resolution expression analysis, Nature Biotech. 21(6):652-659) tomodify mouse genomic Bacterial Artificial Chromosome (BAC) libraries toinactivate the mouse κ and λ light chain loci.

Deletion of the Mouse λ Light Chain Locus.

DNA from mouse BAC clone RP23-135k15 (Invitrogen) was modified byhomologous recombination to inactivate the endogenous mouse λ lightchain locus through targeted deletion of the Vλ-Jλ-Cλ gene clusters(FIG. 2).

Briefly, the entire proximal cluster comprising Vλ1-Jλ3-Cλ3-Jλ1-Cλ1 genesegments was deleted in a single targeting event using a targetingvector comprising a neomycin cassette flanked by IoxP sites with a 5′mouse homology arm containing sequence 5′ of the Vλ1 gene segment and a3′ mouse homology arm containing sequence 3′ of the Cλ1 gene segment(FIG. 2, Targeting Vector 1).

A second targeting construct was prepared to precisely delete the distalendogenous mouse L gene cluster containing Vλ2-Jλ2-Cλ2-Jλ4-Cλ4 exceptthat the targeting construct contained a 5′ mouse homology arm thatcontained sequence 5′ of the Vλ2 gene segment and a 3′ mouse homologyarm that contained sequence 5′ to the endogenous Cλ2 gene segment (FIG.2, Targeting Vector 2). Thus, the second targeting construct preciselydeleted Vλ2-Jλ2, while leaving Cλ2-Jλ4-Cλ4 intact at the endogenousmouse λ locus. ES cells containing an inactivated endogenous λ locus (asdescribed above) were confirmed by karyotyping and screening methods(e.g., TAQMAN®) known in the art. DNA was then isolated from themodified ES cells and subjected to treatment with CRE recombinasethereby mediating the deletion of the proximal targeting cassettecontaining the neomycin marker gene, leaving only a single IoxP site atthe deletion point (FIG. 2, bottom).

Deletion of the Mouse κ Light Chain Locus.

Several targeting constructs were made using similar methods describedabove to modify DNA from mouse BAC clones RP23-302g12 and RP23-254m04(Invitrogen) by homologous recombination to inactivate the mouse κ lightchain locus in a two-step process (FIG. 3).

Briefly, the Jκ gene segments (1-5) of the endogenous mouse κ lightchain locus were deleted in a single targeting event using a targetingvector comprising a hygromycin-thymidine kinase (hyg-TK) cassettecontaining a single IoxP site 3′ to the hyg-TK cassette (FIG. 3, JκTargeting Vector). The homology arms used to make this targeting vectorcontained mouse genomic sequence 5′ and 3′ of the endogenous mouse Jκgene segments. In a second targeting event, a second targeting vectorwas prepared to delete a portion of mouse genomic sequence upstream (5′)to the most distal endogenous mouse Vκ gene segment (FIG. 3, VκTargeting Vector). This targeting vector contained an inverted Iox511site, a IoxP site and a neomycin cassette. The homology arms used tomake this targeting vector contained mouse genomic sequence upstream ofthe most distal mouse Vκ gene segment. The targeting vectors were usedin a sequential fashion (i.e., Jκ then Vκ) to target DNA in ES cells. ESbearing a double-targeted chromosome (i.e., a single endogenous mouse κlocus targeted with both targeting vectors) were confirmed bykaryotyping and screening methods (e.g., Taqman™) known in the art. DNAwas then isolated from the modified ES cells and subjected to treatmentwith Cre recombinase thereby mediating the deletion of endogenous mouseVκ gene segments and both selection cassettes, while leaving twojuxtaposed Iox sites in opposite orientation relative to one another(FIG. 3, bottom; SEQ ID NO:1).

Thus, two modified endogenous light chain loci (κ and λ) containingintact enhancer and constant regions were created for progressivelyinserting unrearranged human λ germline gene segments in a precisemanner using targeting vectors described below.

Example II Replacement of Mouse Light Chain Loci with a Human λ LightChain Mini-Locus

Multiple targeting vectors were engineered for progressive insertion ofhuman λ gene segments into the endogenous mouse κ and λ light chain lociusing similar methods as described above. Multiple independent initialmodifications were made to the endogenous light chain loci eachproducing a chimeric light chain locus containing hVλ and Jλ genesegments operably linked to mouse light chain constant genes andenhancers.

A Human λ Mini-Locus Containing 12 Human Vλ and One Human Jλ GeneSegment.

A series of initial targeting vectors were engineered to contain thefirst 12 consecutive human V└ gene segments from cluster A and a hJλ1gene segment or four hJλ gene segments using a human BAC clone namedRP11-729g4 (Invitrogen). FIGS. 4A and 4B show the targeting vectors thatwere constructed for making an initial insertion of human λ light chaingene segments at the mouse λ and κ light chain loci, respectively.

For a first set of initial targeting vectors, a 124,125 bp DNA fragmentfrom the 729g4 BAC clone containing 12 hVλ gene segments and a hJλ1 genesegment was engineered to contain a PI-Scel site 996 bp downstream (3′)of the hJλ1 gene segment for ligation of a 3′ mouse homology arm. Twodifferent sets of homology arms were used for ligation to this humanfragment; one set of homology arms contained endogenous mouse λsequences from the 135k15 BAC clone (FIG. 4A) and another set containedendogenous κ sequence 5′ and 3′ of the mouse Vκ and Jκ gene segmentsfrom mouse BAC clones RP23-302g12 and RP23-254m04, respectively (FIG.4B).

For the 12/1-λ Targeting Vector (FIG. 4A), a PI-Scel site was engineeredat the 5′ end of a 27,847 bp DNA fragment containing the mouseCλ2-Jλ4-Cλ4 and enhancer 2.4 of the modified mouse λ locus described inExample 1. The ˜28 kb mouse fragment was used as a 3′ homology arm byligation to the ˜124 kb human λ fragment, which created a 3′ junctioncontaining, from 5′ to 3′, a hJλ1 gene segment, 996 bp of human λsequence 3′ of the hJλ1 gene segment, 1229 bp of mouse λ sequence 5′ tothe mouse Cλ2 gene, the mouse Cλ2 gene and the remaining portion of the˜28 kb mouse fragment. Upstream (5′) from the human Vλ3-12 gene segmentwas an additional 1456 bp of human λ sequence before the start of the 5′mouse homology arm, which contained 23,792 bp of mouse genomic DNAcorresponding to sequence 5′ of the endogenous mouse λ locus. Betweenthe 5′ homology arm and the beginning of the human λ sequence was aneomycin cassette flanked by Frt sites.

Thus, the 12/1-λ Targeting Vector included, from 5′ to 3′, a 5′ homologyarm containing ˜24 kb of mouse λ genomic sequence 5′ of the endogenous λlocus, a 5′ Frt site, a neomycin cassette, a 3′ Frt site, ˜123 kb ofhuman genomic λ sequence containing the first 12 consecutive hVλ genesegments and a hJλ1 gene segment, a PI-Scel site, and a 3′ homology armcontaining ˜28 kb of mouse genomic sequence including the endogenousCλ2-Jλ4-Cλ4 gene segments, the mouse enhancer 2.4 sequence andadditional mouse genomic sequence downstream (3′) of the enhancer 2.4(FIG. 4A).

In a similar fashion, the 12/1-κ Targeting Vector (FIG. 4B) employed thesame ˜124 human λ fragment with the exception that mouse homology armscontaining mouse κ sequence were used such that targeting to theendogenous κ locus could be achieved by homologous recombination. Thus,the 12/1-κ Targeting Vector included, from 5′ to 3′, a 5′ homology armcontaining ˜23 kb of mouse genomic sequence 5′ of the endogenous κlocus, an I-Ceul site, a 5′ Frt site, a neomycin cassette, a 3′ Frtsite, ˜124 kb of human genomic λ sequence containing the first 12consecutive hVλ gene segments and a hJλ1 gene segment, a PI-Scel site,and a 3′ homology arm containing ˜28 kb of mouse genomic sequenceincluding the endogenous the mouse Cκ gene, Eκi and Eκ3′ and additionalmouse genomic sequence downstream (3′) of Eκ3′ (FIG. 4B, 12/1-κTargeting Vector).

Homologous recombination with either of these two initial targetingvectors created a modified mouse light chain locus (κ or λ) containing12 hVλ gene segments and a hJλ1 gene segment operably linked to theendogenous mouse light chain constant gene and enhancers (Cκ or Cλ2 andEκi/Eκ3′ or Enh 2.4/Enh 3.1) gene which, upon recombination, leads tothe formation of a chimeric λ light chain.

A human λ mini-locus with 12 human Vλ and four human Jλ gene segments.

In another approach to add diversity to a chimeric λ light chain locus,a third initial targeting vector was engineered to insert the first 12consecutive human Vλ gene segments from cluster A and hJλ1, 2, 3 and 7gene segments into the mouse κ light chain locus (FIG. 4B, 12/4-κTargeting Vector). A DNA segment containing hJλ1, Jλ2, Jλ3 and Jλ7 genesegments was made by de novo DNA synthesis (Integrated DNA Technologies)including each Jλ gene segment and human genomic sequence of ˜100 bpfrom both the immediate 5′ and 3′ regions of each Jλ gene segment. API-Scel site was engineered into the 3′ end of this ˜1 kb DNA fragmentand ligated to a chloroamphenicol cassette. Homology arms were PCRamplified from human λ sequence at 5′ and 3′ positions relative to thehJλ1 gene segment of the human BAC clone 729g4. Homologous recombinationwith this intermediate targeting vector was performed on a modified729g4 BAC clone that had been previously targeted upstream (5′) of thehuman Vλ3-12 gene segment with a neomycin cassette flanked by Frt sites,which also contained an I-Ceul site 5′ to the 5′ Frt site. Thedouble-targeted 729g4 BAC clone included from 5′ to 3′ an I-Ceul site, a5′ Frt site, a neomycin cassette, a 3′ Frt site, a ˜123 kb fragmentcontaining the first 12 hVλ gene segments, a ˜1 kb fragment containinghuman Jλ1, 2, 3 and 7 gene segments, a PI-Scel site, and achloroamphenicol cassette. This intermediate targeting vector wasdigested together with I-Ceul and PI-Scel and subsequently ligated intothe modified mouse BAC clone (described above) to create the thirdtargeting vector.

This ligation resulted in a third targeting vector for insertion ofhuman λ sequences into the endogenous κ light chain locus, whichincluded, from 5′ to 3′, a 5′ mouse homology arm containing ˜23 kb ofgenomic sequence 5′ of the endogenous mouse κ locus, an I-Ceul site, a5′ Frt site, a neomycin cassette, a 3′ Frt site, a ˜123 kb fragmentcontaining the first 12 hVλ gene segments, a ˜1 kb fragment containinghJλ1, 2, 3 and 7 gene segments, a PI-Scel site and a 3′ homology armcontaining ˜28 kb of mouse genomic sequence including the endogenous themouse Cκ gene, Eκi and Eκ3′ and additional mouse genomic sequencedownstream (3′) of Eκ3′ (FIG. 4B, 12/4-κ Targeting Vector). Homologousrecombination with this third targeting vector created a modified mouseκ light chain locus containing 12 hVλ gene segments and four hJλ genesegments operably linked to the endogenous mouse Cκ gene which, uponrecombination, leads to the formation of a chimeric human λ/mouse κlight chain.

A human λ mini-locus with an integrated human κ light chain sequence.

In a similar fashion, two additional targeting vectors similar to thoseengineered to make an initial insertion of human λ gene segments intothe endogenous κ light chain locus (FIG. 4B, 12/1-κ and 12/4-κ TargetingVectors) were engineered to progressively insert human λ light chaingene segments using uniquely constructed targeting vectors containingcontiguous human λ and K genomic sequences. These targeting vectors wereconstructed to include a ˜23 kb human κ genomic sequence naturallylocated between human Vκ4-1 and Jκ1 gene segments. This human κ genomicsequence was specifically positioned in these two additional targetingvectors between human Vλ and human Jλ gene segments (FIG. 4B, 12(κ)1-κand 12(κ)4-κ Targeting Vectors).

Both targeting vectors containing the human κ genomic sequence were madeusing the modified RP11-729g4 BAC clone described above (FIG. 6). Thismodified BAC clone was targeted with a spectinomycin selection cassetteflanked by NotI and AsiSI restriction sites (FIG. 6, top left).Homologous recombination with the spectinomycin cassette resulted in adouble-targeted 729g4 BAC clone which included, from 5′ to 3′, an I-Ceulsite, a 5′ Frt site, a neomycin cassette, a 3′ Frt site, a ˜123 kbfragment containing the first 12 hVλ gene segments, a NotI site about200 bp downstream (3′) to the nonamer sequence of the hVλ3-1 genesegment, a spectinomycin cassette and an AsiSI site. A separate humanBAC clone containing human κ sequence (CTD-2366j12) was targeted twoindependent times to engineer restriction sites at locations betweenhVκ4-1 and hJκ1 gene segments to allow for subsequent cloning of a ˜23kb fragment for ligation with the hVλ gene segments contained in thedouble targeted modified 729g4 BAC clone (FIG. 6, top right).

Briefly, the 2366j12 BAC clone is about 132 kb in size and contains hVκgene segments 1-6, 1-5, 2-4, 7-3, 5-2, 4-1, human κ genomic sequencedown stream of the Vκ gene segments, hJκ gene segments 1-5, the hCκ andabout 20 kb of additional genomic sequence of the human κ locus. Thisclone was first targeted with a targeting vector containing a hygromycincassette flanked by Frt sites and a NotI site downstream (3′) of the 3′Frt site. The homology arms for this targeting vector contained humangenomic sequence 5′ and 3′ of the Vκ gene segments within the BAC clonesuch that upon homologous recombination with this targeting vector, theVκ gene segments were deleted and a NotI site was engineered ˜133 bpdownstream of the hVκ4-1 gene segment (FIG. 6, top right). This modified2366j12 BAC clone was targeted independently with two targeting vectorsat the 3′ end to delete the hJκ gene segments with a chloroamphenicolcassette that also contained either a hJλ1 gene segment, a PI-Scel siteand an AsiSI site or a human λ genomic fragment containing four hJλ genesegments (supra), a PI-Scel site and an AsiSI site (FIG. 6, top right).The homology arms for these two similar targeting vectors containedsequence 5′ and 3′ of the hJκ gene segments. Homologous recombinationwith these second targeting vectors and the modified 2366j12 BAC cloneyielded a double-targeted 2366j12 clone which included, from 5′ to 3′, a5′ Frt site, a hygromycin cassette, a 3′ Frt site, a NotI site, a 22,800bp genomic fragment of the human κ locus containing the intergenicregion between the Vκ4-1 and Jκ1 gene segments, either a hJλ1 genesegment or a human λ genomic fragment containing hJλ1, Jλ2, Jλ3 and Jλ7,a PI-Scel site and a chloroamphenicol cassette (FIG. 6, top right). Twofinal targeting vectors to make the two additional modifications wereachieved by two ligation steps using the double-targeted 729g4 and2366j12 clones.

Double targeted 729g4 and 2366j12 clones were digested with NotI andAsiSI yielding one fragment containing the neomycin cassette and hVλgene segments and another fragment containing the ˜23 kb genomicfragment of the human κ locus containing the intergenic region betweenthe Vκ4-1 and Jκ1 gene segments, either a hJλ1 gene segment or a genomicfragment containing hJλ1, Jλ2, Jλ3 and Jλ7 gene segments, the PI-Scelsite and the chloroamphenicol cassette, respectively. Ligation of thesefragments generated two unique BAC clones containing from 5′ to 3′ thehVλ gene segments, the human κ genomic sequence between the Vκ4-1 andJκ1 gene segments, either a hJλ1 gene segment or a genomic fragmentcontaining hJλ1, Jλ2, Jλ3 and Jλ7 gene segments, a PI-Scel site and achloroamphenicol cassette (FIG. 6, bottom). These new BAC clones werethen digested with I-Ceul and PI-Scel to release the unique fragmentscontaining the upstream neomycin cassette and the contiguous human λ andκ sequences and ligated into a modified mouse BAC clone 302g12 whichcontained from 5′ to 3′ mouse genomic sequence 5′ of the endogenous κlocus, an I-Ceul site, a 5′ Frt site, a neomycin cassette, a 3′ Frtsite, hVλ gene segments (3-12 to 3-1), a NotI site ˜200 bp downstream ofVλ3-1, ˜23 kb of human κ sequence naturally found between the humanVκ4-1 and Jκ1 gene segments, either a hJλ1 gene segment or a genomicfragment containing hJλ1, Jλ2, Jλ3 and Jλ7 gene segments, the mouse Eκi,the mouse Cκ gene and Eκ3′ (FIG. 4, 12hVλ-VκJκ-hJλ1 and 12hVλ-VκJκ-4hJλTargeting Vectors). Homologous recombination with both of thesetargeting vectors created two separate modified mouse κ light chain locicontaining 12 hVλ gene segments, human κ genomic sequence, and eitherone or four hJλ gene segments operably linked to the endogenous mouse Cκgene which, upon recombination, leads to the formation of a chimerichuman λ/mouse κ light chain.

Example III Engineering Additional Human Vλ Genes Segments into a Humana Light Chain Mini-Locus

Additional hVλ gene segments were added independently to each of theinitial modifications described in Example 2 using similar targetingvectors and methods (FIG. 5A, +16-λ Targeting Vector and FIG. 5B, +16-κTargeting Vector).

Introduction of 16 Additional Human Vλ Gene Segments.

Upstream (5′) homology arms used in constructing targeting vectors foradding 16 additional hVλ gene segments to the modified light chain locidescribed in Example 2 contained mouse genomic sequence 5′ of either theendogenous κ or λ light chain loci. The 3′ homology arms were the samefor all targeting vectors and contained human genomic sequenceoverlapping with the 5′ end of the human λ sequence of the modificationsas described in Example 2.

Briefly, two targeting vectors were engineered for introduction of 16additional hVλ gene segments to the modified mouse light chain locidescribed in Example 2 (FIGS. 5A and 5B, +16-λ or +16-κ TargetingVector). A ˜172 kb DNA fragment from human BAC clone RP11-761I13(Invitrogen) containing 21 consecutive hVλ gene segments from cluster Awas engineered with a 5′ homology arm containing mouse genomic sequence5′ to either the endogenous κ or λ light chain loci and a 3′ homologyarm containing human genomic λ sequence. The 5′ mouse κ or λ homologyarms used in these targeting constructs were the same 5′ homology armsdescribed in Example 2 (FIGS. 5A and 5B). The 3′ homology arm included a53,057 bp overlap of human genomic λ sequence corresponding to theequivalent 5′ end of the ˜123 kb fragment of human genomic λ sequencedescribed in Example 2. These two targeting vectors included, from 5′ to3′, a 5′ mouse homology arm containing either ˜23 kb of genomic sequence5′ of the endogenous mouse κ light chain locus or ˜24 kb of mousegenomic sequence 5′ of the endogenous λ light chain locus, a 5′ Frtsite, a hygromycin cassette, a 3′ Frt site and 171,457 bp of humangenomic λ sequence containing 21 consecutive hVλ gene segments, ˜53 kbof which overlaps with the 5′ end of the human λ sequence described inExample 3 and serves as the 3′ homology arm for this targeting construct(FIGS. 5A and 5B, +16-λ or +16-κ Targeting Vectors). Homologousrecombination with these targeting vectors created independentlymodified mouse κ and λ light chain loci each containing 28 hVλ genesegments and a hJλ1 gene segment operably linked to endogenous mouseconstant genes (Cκ or Cλ2) which, upon recombination, leads to theformation of a chimeric light chain.

In a similar fashion, the +16-κ Targeting Vector was also used tointroduce the 16 additional hVλ gene segments to the other initialmodifications described in Example 2 that incorporated multiple hJλ genesegments with and without an integrated human κ sequence (FIG. 4B).Homologous recombination with this targeting vector at the endogenousmouse κ locus containing the other initial modifications created mouse κlight chain loci containing 28 hVλ gene segments and hJλ1, 2, 3 and 7gene segments with and without a human Vκ-Jκ genomic sequence operablylinked to the endogenous mouse OK gene which, upon recombination, leadsto the formation of a chimeric λ-κ light chain.

Introduction of 12 Additional Human Vλ Gene Segments.

Additional hVλ gene segments were added independently to each of themodifications described above using similar targeting vectors andmethods. The final locus structure resulting from homologousrecombination with targeting vectors containing additional hVλ genesegments are shown in FIGS. 7A and 7B.

Briefly, a targeting vector was engineered for introduction of 12additional hVλ gene segments to the modified mouse κ and λ light chainloci described above (FIGS. 5A and 5B, +12-λ or 12-κ Targeting Vectors).A 93,674 bp DNA fragment from human BAC clone RP11-22118 (Invitrogen)containing 12 consecutive hVλ gene segments from cluster B wasengineered with a 5′ homology arm containing mouse genomic sequence 5′to either the endogenous mouse κ or λ light chain loci and a 3′ homologyarm containing human genomic └ sequence. The 5′ homology arms used inthis targeting construct were the same 5′ homology arms used for theaddition of 16 hVλ gene segments described above (FIGS. 5A and 5B). The3′ homology arm was made by engineering a PI-Scel site ˜3431 bp 5′ tothe human Vλ3-29P gene segment contained in a 27,468 bp genomic fragmentof human λ sequence from BAC clone RP11-761113. This PI-Scel site servedas a ligation point to join the ˜94 kb fragment of additional human λsequence to the ˜27 kb fragment of human λ sequence that overlaps withthe 5′ end of the human λ sequence in the previous modification usingthe +16-λ or +16-κ Targeting Vectors (FIGS. 5A and 5B). These twotargeting vectors included, from 5′ to 3′, a 5′ homology arm containingeither ˜23 kb of mouse genomic sequence 5′ of the endogenous κ lightchain locus or ˜24 kb of mouse genomic sequence 5′ of the endogenous λlight chain locus, a 5′ Frt site, a neomycin cassette, a 3′ Frt site and121,188 bp of human genomic λ sequence containing 16 hVλ gene segmentsand a PI-Scel site, ˜27 kb of which overlaps with the 5′ end of thehuman λ sequence from the insertion of 16 addition hVλ gene segments andserves as the 3′ homology arm for this targeting construct (FIGS. 5A and5B, +12-λ or 12-κ Targeting Vectors). Homologous recombination withthese targeting vectors independently created modified mouse κ and λlight chain loci containing 40 hVλ gene segments and human Jλ1 operablylinked to the endogenous mouse constant genes (Cκ or Cλ2) which, uponrecombination, leads to the formation of a chimeric light chain (bottomof FIGS. 5A and 5B).

In a similar fashion, the +12-κ Targeting Vector was also used tointroduce the 12 additional hVλ gene segments to the other initialmodifications that incorporated multiple hJλ gene segments with andwithout an integrated human κ sequence (FIG. 4B). Homologousrecombination with this targeting vector at the endogenous mouse κ locuscontaining the other modifications created a mouse κ light chain locuscontaining 40 hVλ gene segments and hJλ1, 2, 3 and 7 gene segments withand without a human Vκ-Jκ genomic sequence operably linked to theendogenous mouse OK gene which, upon recombination, leads to theformation of a chimeric λ-κ light chain.

Example IV Identification of Targeted ES Cells Bearing Human Light ChainGene Segments

Targeted BAC DNA made according to the foregoing Examples was used toelectroporate mouse ES cells to create modified ES cells for generatingchimeric mice that express human λ light chain gene segments. ES cellscontaining an insertion of unrearranged human λ light chain genesegments were identified by a quantitative TAQMAN® assay. Specificprimers sets and probes were design for insertion of human λ sequencesand associated selection cassettes (gain of allele, GOA), loss ofendogenous mouse sequences and any selection cassettes (loss of allele,LOA) and retention of flanking mouse sequences (allele retention, AR).For each additional insertion of human λ sequences, additional primersets and probes were used to confirm the presence of the additionalhuman λ sequences as well as the previous primer sets and probes used toconfirm retention of the previously targeted human sequences. Table 1sets forth the primers and associated probes used in the quantitativePCR assays. Table 2 sets forth the combinations used for confirming theinsertion of each section of human L light chain gene segments in EScell clones.

ES cells bearing the human λ light chain gene segments are optionallytransfected with a construct that expresses FLP in order to remove theFrt'ed neomycin cassette introduced by the insertion of the targetingconstruct containing human Vλ5-52-Vλ1-40 gene segments (FIGS. 5A and5B). The neomycin cassette may optionally be removed by breeding to micethat express FLP recombinase (e.g., U.S. Pat. No. 6,774,279).Optionally, the neomycin cassette is retained in the mice.

TABLE 1 Primer SEQ ID NO: Probe SEQ ID NO: hL2F 2 hL2P 24 hL2R 3 hL3F 4hL3P 25 hL3R 5 NeoF 6 NeoP 26 NeoR 7 61hJ1F 8 61hJ1P 27 61hJ1R 9 67hT1F10 67hT1P 28 67hT1R 11 67hT3F 12 67hT3P 29 67hT3R 13 HygF 14 HygP 30HygR 15 MKD2F 16 MKD2P 31 MKD2R 17 MKP8F 18 MKP8P 32 MKP8R 19 MKP15F 20MKP15P 33 MKP15R 21 MK20F 22 — — MKP4R 23 68h2F 34 68h2P 38 68h2R 3568h5F 36 68h5P 39 68h5R 37 mL1F 75 mL1P 83 mL1R 76 mL2F 77 mL2P 84 mL2R78 mL11F 79 mL11P 85 mL11R 80 mL12F 81 mL12P 86 mL12R 82

TABLE 2 Forward/Reverse Modification Assay Primer Set Probe SequenceLocation Insertion of GOA hL2F/hL2R hL2P hVλ3-12 − 12 hVλ hL3F/hL3R hL3PhVλ3-1 & hJλ1 61hJ1F/61hJ1R 61hJ1P hJλ sequence NeoF/NeoR NeoP Neomycincassette LOA MK20F/MKP4R — lox511/loxP sequence of inactivated κ locusHygF/HygR HygP Hygromycin cassette from inactivated λ locus mL1F/mL1RmL1P Mouse Vλ1- mL2F/mL2R mL2P Cλ1 Cluster mL11F/mL11R mL11P Mouse Vλ2-mL12F/mL12R mL12P Cλ2 Cluster AR/LOA MKD2F/MKD2R MKD2P Mouse sequence in5′ Vκ locus MKP15F/MKP15R MKP15P Mouse sequence in 3′ Vκ locus Insertionof GOA 67hT1F/67hT1R 67hT1P hVλ3-27 − 16 hVλ 67hT3F/67hT3R 67hT3PhVλ3-12 HygF/HygR HygP Hygromycin cassette LOA NeoF/NeoR NeoP Neomycincassette mL1F/mL1R mL1P Mouse Vλ1- mL2F/mL2R mL2P Cλ1 ClustermL11F/mL11R mL11P Mouse Vλ2- mL12F/mL12R mL12P Cλ2 Cluster AR hL2F/hL2RhL2P hVλ3-12 − hL3F/hL3R hL3P hVλ3-1 AR/LOA MKD2F/MKD2R MKD2P Mousesequence in 5′ Vκ locus MKP15F/MKP15R MKP15P Mouse sequence in 3′ Vκlocus Insertion of GOA 68h2F/68h2R 68h2P hVλ5-52 − 12 hVλ 68h5F/68h5R68h5P hvλ1-40 NeoF/NeoR NeoP Neomycin cassette HygF/HygR HygP Hygromycincassette mL1F/mL1R mL1P Mouse Vλ1- LOA mL2F/mL2R mL2P Cλ1 ClustermL11F/mL11R mL11P Mouse Vλ2- mL12F/mL12R mL12P Cλ2 Cluster hL2F/hL2RhL2P hVλ3-12 − AR hL3F/hL3R hL3P hVλ3-1 67hT1F/67hT1R 67hT1P hVλ3-27 −67hT3F/67hT3R 67hT3P hVλ3-12 AR/LOA MKD2F/MKD2R MKD2P Mouse sequence in5′ Vκ locus MKP15F/MKP15R MKP15P Mouse sequence in 3′ Vκ locus

Example V Generation of Mice Expressing Human A Light Chains From anEndogenous Light Chain Locus

Targeted ES cells described above were used as donor ES cells andintroduced into an 8-cell stage mouse embryo by the VELOCIMOUSE® method(see, e.g., U.S. Pat. No. 7,294,754 and Poueymirou et al. (2007) F0generation mice that are essentially fully derived from the donorgene-targeted ES cells allowing immediate phenotypic analyses NatureBiotech. 25(1):91-99. VELOCIMICE® (F0 mice fully derived from the donorES cell) independently bearing human λ gene segments were identified bygenotyping using a modification of allele assay (Valenzuela et al.,supra) that detected the presence of the unique human λ gene segments(supra).

κ:λ Light Chain Usage of Mice Bearing Human a Light Chain Gene Segments.

Mice homozygous for each of three successive insertions of hVλ genesegments with a single hJλ gene segment (FIG. 5B) and mice homozygousfor a first insertion of hVλ gene segments with either a single hJλ genesegment or four human Jλ gene segments including a human Vκ-Jκ genomicsequence (FIG. 4B) were analyzed for κ and λ light chain expression insplenocytes using flow cytometry.

Briefly, spleens were harvested from groups of mice (ranging from threeto seven animals per group) and grinded using glass slides. Followinglysis of red blood cells (RBCs) with ACK lysis buffer (LonzaWalkersville), splenocytes were stained with fluorescent dye conjugatedantibodies specific for mouse CD19 (Clone 1D3; BD Biosciences), mouseCD3 (17A2; Biolegend), mouse Igκ (187.1; BD Biosciences) and mouse Igλ(RML-42; Biolegend). Data was acquired using a BD™ LSR II flow cytometer(BD Biosciences) and analyzed using FLOWJO™ software (Tree Star, Inc.).Table 3 sets forth the average percent values for B cells (CD19⁺), κlight chain (CD19⁺Igκ⁺Igλ⁻), and λ light chain (CD19⁺Igκ⁻Igλ⁺)expression observed in splenocytes from groups of animals bearing eachgenetic modification.

In a similar experiment, B cell contents of the splenic compartment frommice homozygous for a first insertion of 12 hVλ and four hJλ genesegments including a human Vκ-Jκ genomic sequence operably linked to themouse Cκ gene (bottom of FIG. 4B) and mice homozygous for 40 hVλ and onehJλ gene segment (bottom of FIG. 5B or top of FIG. 7B) were analyzed forIgκ and Igλ expression using flow cytometry (as described above). FIG.8A shows the Igλ and Igκ expression in CD19⁺ B cells for arepresentative mouse from each group. The number of CD19⁺ B cells perspleen was also recorded for each mouse (FIG. 8B).

In another experiment, B cell contents of the spleen and bone marrowcompartments from mice homozygous for 40 hVλ and four hJλ gene segmentsincluding a human Vκ-Jκ genomic sequence operably linked to the mouse Cκgene (bottom of FIG. 7B) were analyzed for progression through B celldevelopment using flow cytometry of various cell surface markers.

Briefly, two groups (N=3 each, 9-12 weeks old, male and female) of wildtype and mice homozygous for 40 hVλ and four hJλ gene segments includinga human Vκ-Jκ genomic sequence operably linked to the mouse Cκ gene weresacrificed and spleens and bone marrow were harvested. Bone marrow wascollected from femurs by flushing with complete RPMI medium (RPMI mediumsupplemented with fetal calf serum, sodium pyruvate, Hepes,2-mercaptoethanol, non-essential amino acids, and gentamycin). RBCs fromspleen and bone marrow preparations were lysed with ACK lysis buffer(Lonza Walkersville), followed by washing with complete RPMI medium.1×10⁶ cells were incubated with anti-mouse CD16/CD32 (2.4G2, BDBiosciences) on ice for 10 minutes, followed by labeling with a selectedantibody panel for 30 min on ice.

Bone marrow panel: anti-mouse FITC-CD43 (1B11, BioLegend), PE-ckit (2B8,BioLegend), PeCy7-IgM (11/41, eBioscience), PerCP-Cy5.5-IgD (11-26c.2a,BioLegend), APC-B220 (RA3-6B2, eBioscience), APC-H7-CD19 (ID3, BD) andPacific Blue-CD3 (17A2, BioLegend).

Bone marrow and spleen panel: anti-mouse FITC-Igκ (187.1, BD), PE-Igλ(RML-42, BioLegend), PeCy7-IgM (11/41, ebioscience), PerCP-Cy5.5-IgD(11-26c.2a, BioLegend), Pacific Blue-CD3 (17A2, BioLegend), APC-B220(RA3-6B2, eBioscience), APC-H7-CD19 (ID3, BD).

Following staining, cells were washed and fixed in 2% formaldehyde. Dataacquisition was performed on a FACSCANTOII™ flow cytometer (BDBiosciences) and analyzed with FLOWJO™ software (Tree Star, Inc.). FIGS.9A-9D show the results for the splenic compartment of one representativemouse from each group. FIGS. 10A-10E show the results for the bonemarrow compartment of one representative mouse from each group. Table 4sets forth the average percent values for B cells (CD19⁺), κ light chain(CD19⁺Igκ⁺Igλ⁻), and λ light chain (CD19⁺Igκ⁻Igλ⁺) expression observedin splenocytes from groups of animals bearing various geneticmodifications. Table 5 sets forth the average percent values for B cells(CD19⁺), mature B cells (B220^(hi)IgM⁺), immature B cells(B220^(int)IgM⁺), immature B cells expressing κ light chain(B220^(int)IgM⁺Igκ⁺) and immature B cells expressing λ light chain(B220^(int)IgM⁺Igλ⁺) observed in bone marrow of wild type and micehomozygous for 40 hVλ and four hJλ gene segments including a human Vκ-Jκgenomic sequence operably linked to the mouse Cκ gene. This experimentwas repeated with additional groups of the mice described above anddemonstrated similar results (data not shown).

TABLE 3 Genotype % B cells % Igκ⁺ % Igλ⁺ Wild Type 46.2 91.0 3.6 12hVλ + hJλ1 28.3 10.4 62.5 12 hVλ − VκJκ − hJλ1 12.0 11.0 67.5 12 hVλ −VκJκ − 4hJλ 41.8 17.2 68.4 28 hVλ + hJλ1 22.0 13.3 51.1 40 hVλ + hJλ128.2 24.3 53.0

TABLE 4 Genotype % B cells % Igκ⁺ % Igλ⁺ Wild Type 49.8 91.2 3.5 40 hVλ− VκJκ − 4hJλ 33.3 41.6 43.1

TABLE 5 % % % % % B Mature Immature Immature Immature Genotype cells Bcells B cells Igκ⁺ B cells Igλ⁺ B cells Wild Type 62.2 9.2 12.0 79.08.84 40hVλ − VκJκ − 4hJλ 60.43 2.59 7.69 38.29 43.29

Human Vλ Gene Usage in Mice Bearing Human Light Chain Gene Segments.

Mice heterozygous for a first insertion of human λ sequences(hVλ3-12-hVλ3-1 and hJλ1, FIG. 5B) and homozygous for a third insertionof human λ sequences (hVλ5-52-hVλ3-1 and hJλ1, FIG. 5B) were analyzedfor human λ light chain gene usage by reverse-transcriptase polymerasechain reaction (RT-PCR) using RNA isolated from splenocytes.

Briefly, spleens were harvested and perfused with 10 mL RPMI-1640(Sigma) with 5% HI-FBS in sterile disposable bags. Each bag containing asingle spleen was then placed into a STOMACHER™ (Seward) and homogenizedat a medium setting for 30 seconds. Homogenized spleens were filteredusing a 0.7 μm cell strainer and then pelleted with a centrifuge (1000rpm for 10 minutes) and RBCs were lysed in BD PHARM LYSE™ (BDBiosciences) for three minutes. Splenocytes were diluted with RPMI-1640and centrifuged again, followed by resuspension in 1 mL of PBS (IrvineScientific). RNA was isolated from pelleted splenocytes using standardtechniques known in the art.

RT-PCR was performed on splenocyte RNA using primers specific for humanhVλ gene segments and the mouse Cκ gene (Table 6). PCR products weregel-purified and cloned into pCR2.1-TOPO TA vector (Invitrogen) andsequenced with primers M13 Forward (GTAAAACGAC GGCCAG; SEQ ID NO:55) andM13 Reverse (CAGGAAACAG CTATGAC; SEQ ID NO:56) located within the vectorat locations flanking the cloning site. Eighty-four total clones derivedfrom the first and third insertions of human λ sequences were sequencedto determine hVλ gene usage (Table 7). The nucleotide sequence of thehVλ-hJλ1-mCκ junction for selected RT-PCR clones is shown in FIG. 11.

In a similar fashion, mice homozygous for a third insertion of human λlight chain gene sequences (i.e. 40 hVλ gene segments and four hJλ genesegments including a human Vκ-Jκ genomic sequence, bottom of FIG. 7B)operably linked to the endogenous mouse Cκ gene were analyzed for humanλ light chain gene usage by RT-PCR using RNA isolated from splenocytes(as described above). The human λ light chain gene segment usage for 26selected RT-PCR clones are shown in Table 8. The nucleotide sequence ofthe hVλ-hJλ-mCκ junction for selected RT-PCR clones is shown in FIG. 12.

In a similar fashion, mice homozygous for a first insertion of human λlight chain gene segments (12 hVλ gene segments and hJλ1, FIGS. 4A &FIG. 5A) operably linked to the endogenous mouse Cλ2 gene were analyzedfor human λ light chain gene usage by RT-PCR using RNA isolated fromsplenocytes (as described above). The primers specific for hVλ genesegments (Table 6) were paired with one of two primers specific for themouse Cλ2 gene; Cλ2-1 (SEQ ID NO:104) or Cλ2-2 (SEQ ID NO:105).

Multiple hVλ gene segments rearranged to hλ1 were observed from theRT-PCR clones from mice bearing human λ light chain gene segments at theendogenous mouse λ light chain locus. The nucleotide sequence of thehVλ-hJλ-mCλ2 junction for selected RT-PCR clones is shown in FIG. 13.

TABLE 6 SEQ ID Sequence (5′-3′) NO: 5′ hVλ Primer VLL-1CCTCTCCTCC TCACCCTCCT 40 VLL-1n ATGRCCDGST YYYCTCTCCT 41 VLL-2CTCCTCACTC AGGGCACA 42 VLL-2n ATGGCCTGGG CTCTGCTSCT 43 VLL-3ATGGCCTGGA YCSCTCTCC 44 VLL-4 TCACCATGGC YTGGRYCYCM YTC 45 VLL-4.3TCACCATGGC CTGGGTCTCC TT 46 VLL-5 TCACCATGGC CTGGAMTCYT CT 47 VLL-6TCACCATGGC CTGGGCTCCA CTACTT 48 VLL-7 TCACCATGGC CTGGACTCCT 49 VLL-8TCACCATGGC CTGGATGATG CTT 50 VLL-9 TAAATATGGC CTGGGCTCCT CT 51 VLL-10TCACCATGCC CTGGGCTCTG CT 52 VLL-11 TCACCATGGC CCTGACTCCT CT 53 3′ MouseCκ Primer mIgKC3′-1 CCCAAGCTTA CTGGATGGTG  54 GGAAGATGGA

TABLE 7 hVλ Observed No. of Clones 3-1  2 4-3  3 2-8  7 3-9  4 3-10 32-14 1 3-19 1 2-23 7 3-25 1 1-40 9 7-43 2 1-44 2 5-45 8 7-46 3 9-49 61-51 3

TABLE 8 Clone hVλ hJλ 1-3 1-44 7 1-5 1-51 3 2-3 9-49 7 2-5 1-40 1 2-61-40 7 3b-5  3-1  7 4a-1  4-3  7 4a-5  4-3  7 4b-1  1-47 3 5-1 3-10 35-2 1-40 7 5-3 1-40 7 5-4 7-46 2 5-6 1-40 7 5-7 7-43 3 6-1 1-40 1 6-21-40 2 6-7 1-40 3 7a-1  3-10 7 7a-2  9-49 2 7a-7  3-10 7 7b-2  7-43 37b-7  7-46 7 7b-8  7-43 3 11a-1  5-45 2 11a-2  5-45 7

FIG. 11 shows the sequence of the hVλ-hJλ1-mCκ junction for RT-PCRclones from mice bearing a first and third insertion of hVλ genesegments with a single hJλ gene segment. The sequences shown in FIG. 11illustrate unique rearrangements involving different hVλ gene segmentswith hJλ1 recombined to the mouse Cκ gene. Heterozygous mice bearing asingle modified endogenous κ locus containing 12 hVλ gene segments andhJλ1 and homozygous mice bearing two modified endogenous κ locicontaining 40 hVλ gene segments and hJλ1 were both able to produce humanλ gene segments operably linked to the mouse Cκ gene and produce B cellsthat expressed human λ light chains. These rearrangements demonstratethat the chimeric loci were able to independently rearrange human λ genesegments in multiple, independent B cells in these mice. Further, thesemodifications to the endogenous κ light chain locus did not render anyof the hVλ gene segments inoperable or prevent the chimeric locus fromrecombining multiple hVλ and a hJλ (Jλ1) gene segment during B celldevelopment as evidenced by 16 different hVλ gene segments that wereobserved to rearrange with hJλ1 (Table 7). Further, these mice madefunctional antibodies containing rearranged human Vλ-Jλ gene segmentsoperably linked to mouse Cκ genes as part of the endogenousimmunoglobulin light chain repertoire.

FIG. 12 shows the sequence of the hVλ-hJλ-mCκ junction for selectedRT-PCR clones from mice homozygous for 40 hVλ and four hJλ gene segmentsincluding a human Vκ-Jκ genomic sequence. The sequences shown in FIG. 12illustrate additional unique rearrangements involving multiple differenthVλ gene segments, spanning the entire chimeric locus, with multipledifferent hJλ gene segments rearranged and operably linked to the mouseCκ gene. Homozygous mice bearing modified endogenous κ loci containing40 hVλ and four hJλ gene segments were also able to produce human λ genesegments operably linked to the mouse Cκ gene and produce B cells thatexpressed human λ light chains. These rearrangements further demonstratethat the all stages of chimeric loci were able to independentlyrearrange human λ gene segments in multiple, independent B cells inthese mice. Further, these additional modifications to the endogenous Klight chain locus demonstrates that each insertion of human λ genesegments did not render any of the hVλ and/or Jλ gene segmentsinoperable or prevent the chimeric locus from recombining the hVλ and Jλgene segments during B cell development as evidenced by 12 different hVλgene segments that were observed to rearrange with all four hJλ genesegments (Table 8) from the 26 selected RT-PCR clone. Further, thesemice as well made functional antibodies containing human Vλ-Jλ genesegments operably linked to mouse Cκ regions as part of the endogenousimmunoglobulin light chain repertoire.

FIG. 13 shows the sequence of the hVλ-hJλ-mCλ2 junction for threeindividual RT-PCR clones from mice homozygous for 12 hVλ gene segmentsand hJλ1. The sequences shown in FIG. 13 illustrate additional uniquerearrangements involving different hVλ gene segments, spanning thelength of the first insertion, with hJλ1 rearranged and operably linkedto the mouse Cλ2 gene (2D1=Vλ2-8Jλ1; 2D9=Vλ3-10Jλ1; 3E15=Vλ3-1Jλ1). Oneclone demonstrated a nonproductive rearrangement due to N additions atthe hVλ-hJλ junction (2D1, FIG. 13). This is not uncommon in V(D)Jrecombination, as the joining of gene segments during recombination hasbeen shown to be imprecise. Although this clone represents anunproductive recombinant present in the light chain repertoire of thesemice, this demonstrates that the genetic mechanism that contributes tojunctional diversity among antibody genes is operating normally in thesemice and leading to an antibody repertoire containing light chains withgreater diversity.

Homozygous mice bearing modified endogenous λ loci containing 12 hVλgene segments and hJλ1 were also able to produce human λ gene segmentsoperably linked to an endogenous mouse Cλ gene and produce B cells thatexpressed reverse chimeric λ light chains containing hVλ regions linkedto mouse Cλ regions. These rearrangements further demonstrate that humanλ light chain gene segments placed at the other light chain locus (i.e.,the λ locus) were able to independently rearrange human λ gene segmentsin multiple, independent B cells in these mice. Further, themodifications to the endogenous λ light chain locus demonstrate that theinsertion of human λ gene segments did not render any of the hVλ and/orhJλ1 gene segments inoperable or prevent the chimeric locus fromrecombining the hVλ and hJλ1 gene segments during B cell development.Further, these mice also made functional antibodies containing humanVλ-Jλ gene segments operably linked to a mouse Cλ region as part of theendogenous immunoglobulin light chain repertoire.

As shown in this Example, mice bearing human λ light chain gene segmentsat the endogenous κ and λ light chain loci are capable of rearranginghuman λ light chain gene segments and expressing them in the context ofa mouse Cκ and/or Cλ region as part of the normal antibody repertoire ofthe mouse because a functional light chain is required at variouscheckpoints in B cell development in both the spleen and bone marrow.Further, early subsets of B cells (e.g., pre-, pro- and transitional Bcells) demonstrate a normal phenotype in these mice as compared to wildtype littermates (FIGS. 9D, 10A and 10B). A small deficit in bone marrowand peripheral B cell populations was observed, which may be attributedto a deletion of a subset of auto-reactive immature B cells and/or asuboptimal association of human λ light chain with mouse heavy chain.However, the Igκ/Igλ usage observed in these mice demonstrates asituation that is more like human light chain expression than thatobserved in mice.

Example VI Breeding of Mice Expressing Human A, Light Chains From anEndogenous Light Chain Locus

To optimize the usage of the human λ gene segments at an endogenousmouse light chain locus, mice bearing the unrearranged human λ genesegments are bred to another mouse containing a deletion in the opposingendogenous light chain locus (either κ or λ). For example, human λ genesegments positioned at the endogenous κ locus would be the onlyfunctional light chain gene segments present in a mouse that alsocarried a deletion in the endogenous λ light chain locus. In thismanner, the progeny obtained would express only human λ light chains asdescribed in the foregoing examples. Breeding is performed by standardtechniques recognized in the art and, alternatively, by commercialcompanies, e.g., The Jackson Laboratory. Mouse strains bearing human λlight chain gene segments at the endogenous κ locus and a deletion ofthe endogenous λ light chain locus are screened for presence of theunique reverse-chimeric (human-mouse) λ light chains and absence ofendogenous mouse λ light chains.

Mice bearing an unrearranged human λ light chain locus are also bredwith mice that contain a replacement of the endogenous mouse heavy chainvariable gene locus with the human heavy chain variable gene locus (seeU.S. Pat. No. 6,596,541, Regeneron Pharmaceuticals, the VELOCIMMUNE®genetically engineered mouse). The VELOCIMMUNE® mouse includes, in part,having a genome comprising human heavy chain variable regions operablylinked to endogenous mouse constant region loci such that the mouseproduces antibodies comprising a human heavy chain variable region and amouse heavy chain constant region in response to antigenic stimulation.The DNA encoding the variable regions of the heavy chains of theantibodies can be isolated and operably linked to DNA encoding the humanheavy chain constant regions. The DNA can then be expressed in a cellcapable of expressing the fully human heavy chain of the antibody. Upona suitable breeding schedule, mice bearing a replacement of theendogenous mouse heavy chain locus with the human heavy chain locus andan unrearranged human λ light chain locus at the endogenous κ lightchain locus is obtained. Antibodies containing somatically mutated humanheavy chain variable regions and human λ light chain variable regionscan be isolated upon immunization with an antigen of interest.

Example VII Generation of Antibodies From Mice Expressing Human HeavyChains and Human A Light Chains

After breeding mice that contain the unrearranged human λ light chainlocus to various desired strains containing modifications and deletionsof other endogenous Ig loci (as described above), selected mice areimmunized with an antigen of interest.

Generally, a VELOCIMMUNE® mouse containing one of the single rearrangedhuman germline light chain regions is challenged with an antigen, andlymphatic cells (such as B-cells) are recovered from serum of theanimals. The lymphatic cells may be fused with a myeloma cell line toprepare immortal hybridoma cell lines, and such hybridoma cell lines arescreened and selected to identify hybridoma cell lines that produceantibodies containing human heavy chain and human λ light chain that arespecific to the antigen used for immunization. DNA encoding the variableregions of the heavy chains and the λ light chains may be isolated andlinked to desirable isotypic constant regions of the heavy chain andlight chain. Due to the presence of the additional hVλ gene segments ascompared to the endogenous mouse λ locus, the diversity of the lightchain repertoire is dramatically increased and confers higher diversityon the antigen-specific repertoire upon immunization. The resultingcloned antibody sequences may be subsequently produced in a cell, suchas a CHO cell. Alternatively, DNA encoding the antigen-specific chimericantibodies or the variable domains of the light and heavy chains may beisolated directly from antigen-specific lymphocytes (e.g., B cells).

Initially, high affinity chimeric antibodies are isolated having a humanvariable region and a mouse constant region. As described above, theantibodies are characterized and selected for desirable characteristics,including affinity, selectivity, epitope, etc. The mouse constantregions are replaced with a desired human constant region to generatethe fully human antibody containing a somatically mutated human heavychain and a human λ light chain derived from an unrearranged human λlight chain locus of the invention. Suitable human constant regionsinclude, for example wild type or modified IgG1, IgG2, IgG3, or IgG4.

We claim:
 1. A method for making an antibody comprising a human lightchain variable domain, the method comprising the steps of: (a) exposinga genetically modified mouse to an antigen, wherein the geneticallymodified mouse has a genome that comprises: (i) a first light chainallele comprising human Vλ and Jλ gene segments operably linked to anendogenous mouse CK gene such that the mouse expresses an immunoglobulinlight chain that comprises a human λ variable domain sequence fused witha mouse K constant domain; and (ii) a second light chain allelecomprising human VK and JK gene segments operably linked to anendogenous mouse CK gene such that the mouse expresses an immunoglobulinlight chain that comprises a human K variable domain sequence fused witha mouse K constant domain; (b) allowing the genetically modified mouseto develop an immune response to the antigen; and (c) isolating from themouse of (b) an antibody specific to the antigen, wherein the antibodycomprises a human light chain variable domain derived from (1) the humanVλ and Jλ gene segments or (2) the human VK and JK gene segments.
 2. Themethod of claim 1, wherein the human Vλ and Jλ gene segments comprise atleast 12 human Vλ gene segments.
 3. The method of claim 1, wherein thehuman Vλ and Jλ gene segments comprise at least 28 human Vλ genesegments.
 4. The method of claim 1, wherein the human Vλ and Jλ genesegments comprise at least 40 human Vλ gene segments.
 5. The method ofclaim 1, wherein the human Vλ and Jλ gene segments comprise a human Jλ1gene segment.
 6. The method of claim 1, wherein the mouse furthercomprises a human Vκ-Jκ intergenic region sequence located between thehuman Vλ gene segments and the human Jλ gene segments, wherein the Vκ-Jκintergenic region is the region located about 130 bp downstream of the3′ untranslated region of a human Vκ4-1 gene segment to about 600 bpupstream of a human Jκ1 gene segment as found in a human genome.
 7. Themethod of claim 6, wherein the human Vκ-Jκ intergenic region sequencecomprises SEQ ID NO:
 100. 8. The method of claim 1, the mouse furthercomprises an immunoglobulin heavy chain allele comprising human V_(H),D_(H), and J_(H) gene segments operably linked to an endogenous mouseheavy chain constant region gene such that the mouse expresses animmunoglobulin heavy chain that comprises a human heavy chain variabledomain sequence fused with a mouse heavy chain constant domain.
 9. Themethod of claim 8, wherein the mouse further comprises a human Vκ-Jκintergenic region sequence located between the human Vλ gene segmentsand the human JA gene segments, wherein the Vκ-Jκ intergenic region isthe region located about 130 bp downstream of the 3′ untranslated regionof a human Vκ4-1 gene segment to about 600 bp upstream of a human Jκ1gene segment as found in a human genome.
 10. The method of claim 9,wherein the human Vκ-Jκ intergenic region sequence comprises SEQ ID NO:100.
 11. The method of claim 1, wherein the mouse does not express alight chain that comprises a λ constant region.
 12. A method for cloninga light chain variable domain, comprising the steps of: (a) obtaining acell from a genetically modified mouse whose genome comprises: (i) afirst light chain allele comprising human Vλ and Jλ gene segmentsoperably linked to an endogenous mouse CK gene such that the mouseexpresses an immunoglobulin light chain that comprises a human λvariabledomain sequence fused with a mouse K constant domain; and (ii) a secondlight chain allele comprising human VK and JK gene segments operablylinked to an endogenous mouse CK gene such that the mouse expresses animmunoglobulin light chain that comprises a human K variable domainsequence fused with a mouse K constant domain; and (b) cloning a lightchain variable domain derived from either the human Vλ and Jλ genesegments or the human VK and JK gene segments.
 13. The method of claim12, wherein the human Vλ and Jλ gene segments comprise at least 12 humanVλ gene segments.
 14. The method of claim 12, wherein the human Vλ andJλ gene segments comprise at least 28 human Vλ gene segments.
 15. Themethod of claim 12, wherein the human Vλ and Jλ gene segments compriseat least 40 human Vλ gene segments.
 16. The method of claim 12, whereinthe human Vλ and Jλ gene segments comprise a human Jλ1 gene segment. 17.The method of claim 12, wherein the mouse further comprises a humanVκ-Jκ intergenic region sequence located between the human Vλ genesegments and the human Jλ gene segments, wherein the Vκ-Jκ intergenicregion is the region located about 130 bp downstream of the 3′untranslated region of a human Vκ4-1 gene segment to about 600 bpupstream of a human Jκ1 gene segment as found in a human genome.
 18. Themethod of claim 17, wherein the human Vκ-Jκ intergenic region sequencecomprises SEQ ID NO:
 100. 19. The method of claim 12, the mouse furthercomprises an immunoglobulin heavy chain allele comprising human V_(H),D_(H), and J_(H) gene segments operably linked to an endogenous mouseheavy chain constant region gene such that the mouse expresses animmunoglobulin heavy chain that comprises a human heavy chain variabledomain sequence fused with a mouse heavy chain constant domain.
 20. Themethod of claim 12, wherein the mouse does not express a light chainthat comprises a λ constant region.